Lipopolysaccharide-induced proliferation and adhesion of U937 cells to endothelial cells involves barium chloride sensitive hyperpolarization.
The adhesion of monocytes to the endothelium and their proliferation in the subendothelial space play an important role in atherosclerosis. Since the proliferation and migration of cells are influenced by the activity of ion channels, the aim of this study was to examine whether barium chloride (Ba(2+))-sensitive potassium channels (K(iCa)) are involved in lipopolysaccharide (LPS)-induced proliferation of monocytic U937 cells, and in the adhesion of these cells to endothelial cells. The adhesion of LPS-stimulated U937 cells to endothelial cells reached a maximum at a concentration of 5 microg/ml. This effect of LPS was completely abolished in the presence of Ba(2+) (100 micromol/l). In addition, LPS-induced proliferation was significantly reduced by Ba(2+) (control, 100%; LPS 5 microg/ml, 175%; LPS + Ba(2+) 100 micromol/l, 136%; n = 12, P < 0.05). To examine whether K(iCa) are activated by LPS, changes of U937 membrane potential were determined. LPS (5 microg/ml) caused a hyperpolarization of U937 cells indicating a flux of K(+) ions out of the cells. This effect was completely blocked by Ba(2+) (100 micromol/l). In conclusion, we demonstrate that LPS activates K(iCa) in U937 cells, which is responsible for LPS-induced adhesion of these cells to endothelial cells, and to the proliferation of U937 cells.
Erdogan
Ali
A
Department of Cardiology and Angiology, Justus-Liebig-University of Giessen, Giessen, Germany. Ali.Erdogan@med.uni-giessen.de
Schaefer
Christian Alexander
CA
Most
Astrid Kerstin
AK
Schaefer
Martina Barbara
MB
Mayer
Konstantin
K
Tillmanns
Harald
H
Kuhlmann
Christoph Ruediger Wolfram
CR
D017609:Barium Compounds / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002712:Chlorides / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004338:Drug Combinations; D004730:Endothelium, Vascular / Q000187:drug effects* / Q000502:physiology; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology*; D009000:Monocytes / Q000187:drug effects* / Q000502:physiology; D024681:Potassium Channels, Calcium-Activated / Q000187:drug effects*; D020298:U937 Cells; D014470:Umbilical Cord / Q000166:cytology
D017609:Barium Compounds; D002712:Chlorides; D004338:Drug Combinations; D008070:Lipopolysaccharides; D024681:Potassium Channels, Calcium-Activated; C024986:barium chloride