High glucose alters apoptosis and proliferation in HEK293 cells by inhibition of cloned BKCa channel

It has been reported that diabetic vascular dysfunction is associated with impaired function of large conductance Ca2+-activated K+ (BKCa) channels. However, it is unclear whether impaired BKCa channel directly participates in regulating diabetic vascular remodeling by altering cell growth in response to hyperglycemia. In the present study, we investigated the specific role of BKCa channel in controlling apoptosis and proliferation under high glucose concentration (25 mM). The cDNA encoding the α+β1 subunit of BKCa channel, hSloα+β1, was transiently transfected into human embryonic kidney 293 (HEK293) cells. Cloned BKCa currents were recorded by both whole-cell and cell-attached patch clamp techniques. Cell apoptosis was assessed with immunocytochemistry and analysis of fragmented DNA by agarose gel electrophoresis. Cell proliferation was investigated by flow cytometry assays, MTT test, and immunocytochemistry. In addition, the expression of anti-apoptotic protein Bcl-2, intracellular Ca2+, and mitochondrial membrane potential (Δψm) were also examined to investigate the possible mechanisms. Our results indicate that inhibition of cloned BKCa channels might be responsible for hyperglycemia-altered apoptosis and proliferation in HEK-hSloα+β1 cells. However, activation of BKCa channel by NS1619 or Tamoxifen significantly induced apoptosis and suppressed proliferation in HEK-hSloα+β1 cells under hyperglycemia condition. When rat cerebral smooth muscle cells were cultured in hyperglycemia, similar findings were observed. Moreover, the possible mechanisms underlying the activation of BKCa channel were associated with decreased expression of Bcl-2, elevation of intracellular Ca2+, and a concomitant depolarization of Δψm in HEK-hSloα+β1 cells. In conclusion, cloned BKCa channel directly regulated apoptosis and proliferation of HEK293 cell under hyperglycemia condition. J. Cell. Physiol. 226: 1660–1675, 2011. © 2010 Wiley-Liss, Inc.