Inhibition of microparticle release triggers endothelial cell apoptosis and detachment.
Endothelial cell cultures contain caspase 3-containing microparticles (EMP), which are reported to form during or after cell detachment. We hypothesize that also adherent endothelial cells release EMP, thus protecting these cells from caspase 3 accumulation, detachment and apoptosis. Human umbilical vein endothelial cells (HUVEC) were incubated with and without inhibitors of microparticle release (Y-27632, calpeptin), both in the absence or presence of additional "external stress", i.e. the apoptotic agent staurosporin (200 nM) or the activating cytokine interleukin (IL)-1alpha (5 ng/ml). Control cultures contained mainly viable adherent cells and minor fractions of apoptotic detached cells and microparticles in the absence of inhibitors. In the presence of inhibitors, caspase 3 accumulated in adherent cells and detachment tended to increase. During incubation with either staurosporin or IL-1alpha in the absence of inhibitors of microparticle release, adherent cells remained viable, and detachment and EMP release increased slightly. In the presence of inhibitors, dramatic changes occurred in staurosporin-treated cultures. Caspase 3 accumulated in adherent cells and >90% of the cells detached within 48 hours. In IL-1alpha-treated cultures no accumulation of caspase 3 was observed in adherent cells, although detachment increased. Scanning electron microscopy studies confirmed the presence of EMP on both adherent and detached cells. Prolonged culture of detached cells indicated a rapid EMP formation as well as some EMP formation at longer culture periods. Inhibition of EMP release causes accumulation of caspase 3 and promotes cell detachment, although the extent depends on the kind of "external stress". Thus, the release of caspase 3-containing microparticles may contribute to endothelial cell survival.
Abid Hussein
Mohammed N
MN
Department of Clinical Chemistry, Academic Medical Centerof the University of Amsterdam, Amsterdam, The Netherlands. mors99@hotmail.com
Böing
Anita N
AN
Sturk
Augueste
A
Hau
Chi M
CM
Nieuwland
Rienk
R
D017209:Apoptosis; D053148:Caspase 3 / Q000378:metabolism; D002448:Cell Adhesion; D002470:Cell Survival; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000166:cytology; D004730:Endothelium, Vascular / Q000166:cytology*; D005089:Exocytosis; D006801:Humans; D010316:Particle Size; D014471:Umbilical Veins / Q000166:cytology
D053148:Caspase 3