title: Dose-dependent activation of Ca2+-activated K+ channels by ethanol contributes to improved endothelial cell functions.
abstract: BACKGROUND
  Regular moderate alcohol (EtOH) intake seems to protect against both coronary artery disease and ischemic stroke, whereas the risk increases with heavy EtOH consumption. Effects of EtOH on endothelial cell function may be relevant to these disparate effects. Potassium channels play an important role in the regulation of endothelial cell functions. Therefore, we investigated whether Ca-activated K channels (BKCa) are modulated by EtOH. Furthermore, we examined whether EtOH-induced changes of endothelial nitric oxide (NO) formation and cell proliferation are due to BKCa activation.
  
  
  METHODS
  The patch-clamp technique was used to investigate BKCa activity in cultured human umbilical vein endothelial cells (HUVEC). NO formation was analyzed by using the fluorescence dye 4,5-diaminofluorescein. Endothelial proliferation was examined by using cell counts and measuring [H]thymidine incorporation.
  
  
  RESULTS
  EtOH dose-dependently (10-150 mmol/liter) modulated BKCa-activity, with the highest increase of open-state probability at a concentration of 50 mmol/liter (n = 13; p < 0.05). Inside-out recordings revealed that this effect was due to direct BKCa activation, whereas open-state probability was not changed in cell-attached recordings after pertussis toxin preincubation. EtOH (10 and 50 mmol/liter) caused a significant increase of NO levels, which was blocked by the highly selective BKCa inhibitor iberiotoxin (100 nmol/l; n = 30; p < 0.05). Higher concentrations of EtOH (100 and 150 mmol/liter) significantly reduced NO synthesis (n = 30; p < 0.05). Both methods revealed a significant increase of HUVEC proliferation, which was inhibited by iberiotoxin (n = 30; p < 0.05). At a concentration of 150 mmol/liter, EtOH caused a significant reduction of endothelial proliferation.
  
  
  CONCLUSIONS
  EtOH directly activates BKCa in HUVEC, leading to an increase of endothelial proliferation and production of NO. These results indicate a possible beneficial effect of low-dose EtOH on endothelial function, whereas higher concentrations must be considered as harmful.
authors.affiliation: Department of Cardiology and Angiology, Justus Liebig University of Giessen, Giessen, Germany. chr_kuhlmann@web.de
authors.forename: Christoph R W
authors.initials: CR
authors.lastname: Kuhlmann
authors.forename: Fang
authors.initials: F
authors.lastname: Li
authors.forename: Dörte W
authors.initials: DW
authors.lastname: Lüdders
authors.forename: Christian A
authors.initials: CA
authors.lastname: Schaefer
authors.forename: Astrid K
authors.initials: AK
authors.lastname: Most
authors.forename: Ulrich
authors.initials: U
authors.lastname: Backenköhler
authors.forename: Thomas
authors.initials: T
authors.lastname: Neumann
authors.forename: Harald
authors.initials: H
authors.lastname: Tillmanns
authors.forename: Bernd
authors.initials: B
authors.lastname: Waldecker
authors.forename: Ali
authors.initials: A
authors.lastname: Erdogan
authors.forename: Johannes
authors.initials: J
authors.lastname: Wiecha
mesh_terms: D049109:Cell Proliferation / Q000187:drug effects; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology*; D000431:Ethanol / Q000494:pharmacology*; D006801:Humans; D009569:Nitric Oxide / Q000502:physiology; D024681:Potassium Channels, Calcium-Activated / Q000502:physiology*
chemical_list: D024681:Potassium Channels, Calcium-Activated; D009569:Nitric Oxide; D000431:Ethanol