An antibody to VEGF upregulates factor VIII via interleukin-1 in activated adrenal cortex-derived capillary endothelial cells.

We have previously shown in an in vitro wounding system of cultured endothelial cells (EC) that vascular endothelial growth factor (VEGF(165)) treatment upregulated the level of factor VIII (FVIII) in the cells facing an experimental wound. The FVIII upregulation induced by VEGF(165) could be abolished by rhuMab VEGF, a humanized antibody that blocks VEGF functions and inhibits tumorigenesis. Because the thrombotic system is actively involved in angiogenesis, we further investigated the effects of rhuMab VEGF on the regulation of FVIII. Although non-disturbed cells distant from a wound were not affected by rhuMab VEGF treatment, FVIII was also significantly upregulated in the cells along the wound in cultures treated with the antibody alone. RhuMab VEGF stimulation of FVIII could be blocked by VEGF(165). When cells were treated with rhuMab VEGF and VEGF(165) combined together, the stimulation or inhibition of FVIII expression was dose-related and dependent on the amount of excess free rhuMab VEGF and rhuMab VEGF:VEGF(165) immune complexes. Thus, both VEGF(165) and rhuMab VEGF used as single reagents enhanced FVIII in activated endothelial cells, while the immune complexes suppressed the upregulation. Following rhuMab VEGF treatment, two distinct activated endothelial subpopulations that differ in their ability to internalize rhuMab VEGF and express interleukin-1 (IL-1) were identified. IL-1beta but not IL-1alpha appeared to be acting as a mediator between the two endothelial subpopulations as the FVIII upregulation induced by rhuMab VEGF could be totally abolished by treatment with type II soluble IL-1 receptor (sIL-1RII).