Neuropilin-1 Modulates p53/Caspases Axis to Promote Endothelial Cell Survival

Vascular permeability factor/vascular endothelial growth factor (VPF/VEGF), one of the crucial pro-angiogenic factors, functions as a potent inhibitor of endothelial cell (EC) apoptosis. Previous progress has been made towards delineating the VPF/VEGF survival signaling downstream of the activation of VEGFR-2. Here, we seek to define the function of NRP-1 in VPF/VEGF-induced survival signaling in EC and to elucidate the concomitant molecular signaling events that are pivotal for our understanding of the signaling of VPF/VEGF. Utilizing two different in vitro cell culture systems and an in vivo zebrafish model, we demonstrate that NRP-1 mediates VPF/VEGF-induced EC survival independent of VEGFR-2. Furthermore, we show here a novel mechanism for NRP-1-specific control of the anti-apoptotic pathway in EC through involvement of the NRP-1-interacting protein (NIP/GIPC) in the activation of PI-3K/Akt and subsequent inactivation of p53 pathways and FoxOs, as well as activation of p21. This study, by elucidating the mechanisms that govern VPF/VEGF-induced EC survival signaling via NRP-1, contributes to a better understanding of molecular mechanisms of cardiovascular development and disease and widens the possibilities for better therapeutic targets

The interaction of platelets with aortic subendothelium: inhibition of adhesion and secretion by prostaglandin I2

Abstract We have studied the effect of prostaglandin I2 on platelet turnover, attachment to the subendothelium, and secretion following balloon deendothelialization of the rabbit aorta. Survival of 51Cr-labeled platelets in the balloon-injured animals remained normal. Thirty minutes after injury, there were 4.52 X 10(6) platelets/sq cm attached to the aortic surface, which was 87% covered by platelets. Although plasma platelet factor 4, as measured by radioimmunoassay, did not rise above the normal level of 6.8 +/- 2.6 ng/ml (mean +/- SEM) during the first hour after balloon injury, platelet factor 4 antigen was detected within the vessel wall by direct immunofluorescence within 30 min of injury. An infusion of 650–850 ng/kg/min prostaglandin I2 completely inhibited platelet aggregation and reduced surface coverage by 84% and platelet attachment by 63%. Animals given 50–100 ng/kg/min prostaglandin I2, which only partially inhibited platelet aggregation, had 70% of the aortic surface covered by platelets. Platelet factor 4 antigen was also detected within the aortic wall. Platelet attachment was normal in animals that had been given 850 ng/kg/min prostaglandin I2 prior to balloon injury but sacrificed after the infusion was stopped and ex vivo platelet aggregation had returned to normal.</jats:p

Tissue-factor coagulant activity of cultured human endothelial and smooth muscle cells and fibroblasts

Abstract The tissue-factor (thromboplastic) activity of cultured human endothelial cells and fibroblasts is low at time of transfer into fresh medium but increases 3–10 fold. Endothelial cells reach peak activity (400 U/10(5) cells) 5–8 hr after subculture. Activity in fibroblast cultures peaks (3000–12,000 U/10(5) cells) 7–12 hr after subculture. After attaining maximum activity, endothelial and fibroblast tissue- factor content decreases in a time course similar to other cells studied in this laboratory, approaching basal levels by 24–50 hr after subculture. If medium over fibroblasts is changed every 12 hr, activity can be sustained at the peak level for an additional day but cannot be maintained at a high level indefinitely. The kinetics of expression of smooth muscle cell tissue factor are markedly different from other cell types. There is always a pronounced lag (30 hr or more) before the activity increases, and then, in most cases, there is no subsequent decline in activity even though the cells are not refed or restimulated. The activity of each of these cell types is cryptic but becomes available after freeze-thaw disruption of cells.</jats:p

Tissue-factor coagulant activity of cultured human endothelial and smooth muscle cells and fibroblasts

The tissue-factor (thromboplastic) activity of cultured human endothelial cells and fibroblasts is low at time of transfer into fresh medium but increases 3–10 fold. Endothelial cells reach peak activity (400 U/10(5) cells) 5–8 hr after subculture. Activity in fibroblast cultures peaks (3000–12,000 U/10(5) cells) 7–12 hr after subculture. After attaining maximum activity, endothelial and fibroblast tissue- factor content decreases in a time course similar to other cells studied in this laboratory, approaching basal levels by 24–50 hr after subculture. If medium over fibroblasts is changed every 12 hr, activity can be sustained at the peak level for an additional day but cannot be maintained at a high level indefinitely. The kinetics of expression of smooth muscle cell tissue factor are markedly different from other cell types. There is always a pronounced lag (30 hr or more) before the activity increases, and then, in most cases, there is no subsequent decline in activity even though the cells are not refed or restimulated. The activity of each of these cell types is cryptic but becomes available after freeze-thaw disruption of cells.</jats:p