Summary
Ebselen, a seleno-organic compound showing glutathione peroxidase-like activity, has
potent anti-inflammatory and anti-oxidant effects. Since selenium deficiency is thought
to be associated with an increased incidence of vascular thrombosis, we studied the
effect of ebselen on blood cell aggregate formation and vessel occlusion in vivo. In individual microvessels of rat cremaster muscle preparations, photochemically
induced thrombus formation was analyzed in detail using intravital fluorescence microscopy.
In ebselen-pretreated animals (30mg/kg ip), venular thrombus formation was significantly
delayed (50% vessel occlusion: 535±34s; initial stasis: 872±82s; complete occlusion:
908±87s) as compared to vehicle-treated controls (416±42; 612±49; 647±51). Moreover,
ebselen significantly prolonged the kinetics of arteriolar thrombus formation and
even completely prevented blood cell aggregate and thrombus formation in 88.9% of
all arterioles studied (p<0.05 vs controls:37.5%). Anti-thrombotic properties of ebselen
could also be observed in a model of ferric chloride-induced microvascular thrombosis,
with a low dose (5mg/kg ip) being as effective as a high dose pretreatment (30mg/kg
ip). As assessed by flow cytometry of platelet P-selectin immunfluorescence, whole
blood isolated from ebselen-treated animals revealed a significantly lower fraction
of P-selectin expressing platelets when compared with that of DMSO-treated controls.
In addition, oxidant stress-induced upregulation of P-selectin on isolated platelets
was found dose-dependently inhibited by increasing concentrations of ebselen (10-100µM).
Moreover, ebselen dose-dependently inhibited H2O2-induced platelet-leukocyte aggregate formation in whole blood in vitro, suggesting that the anti-thrombotic effect of ebselen is achieved by attenuation
of P-selectin dependent platelet-leukocyte aggregation. Thus, ebselen represents preventive
and therapeutic value for disorders with increased risk for oxidant stress-associated
thrombotic events.
Keywords
Thrombosis - platelet - leukocyte - fluorescence microscopy - flow cytometry - oxidant
stress