Abstract 15984: Alternatively Spliced Tissue Factor Exerts Greater Angiogenic Potency than Full-Length Tissue Factor via HIF-1a Induction in Complicated Atherosclerotic Plaques
Introduction: Increasing evidence suggest that angiogenesis is a source of plaque hemorrhage and rupture, responsible for the onset of cardiovascular events. Alternatively Spliced Tissue Factor (asTF) is an angiogenic factor highly expressed by macrophages within complicated (type VI) coronary and carotid human plaques (Giannarelli et al, JACC ’13).
Hypothesis: asTF is a more potent angiogenic factor than Full-length Tissue Factor (fl-TF) via the up-regulation of Hypoxia-Inducible Factor-1α (HIF-1α) through integrin signaling.
Methods: The angiogenic activities of asTF and fl-TF were compared using the in vitro and in vivo Matrigel assays. HUVEC were seeded on Matrigel and exposed to asTF, fl-TF, Lfl-TF (10 nM), VEGF (50 ng/mL) or vehicle. C57Bl6 mice (n=5 per group) were injected with Matrigel admixed with of the same agonists tested in vitro. Tube number in vitro and vessel density (n°/mm2) in vivo were measured. HIF-1α expression induced by asTF (10nM) was tested in HAEC and in human carotid plaques by Western Blot and immunostaining. The effect of anti-αv, anti-α6, anti-β1, anti-β3 integrin blocking antibodies (10 μg/mL) or FAK inhibitor PP2: 10 μM, ERK inhibitor: 10 μM, MEK inhibitor: 20 μM, PI3K inhibitor: 10 μM on asTF angiogenesis was tested.
Results: asTF induces similar angiogenic effect to that of fl-TF in vitro (Figure 1A); however, asTF shows greater angiogenic potential in vivo (Figure 1B). The higher angiogenic activity of asTF appears to be mediated by the specific up-regulation of HIF-1α (Figure C,D). asTF induces HIF-1α via integrin signaling (Figure 1F) and FAK-independent activation of phosphatidylinositol-kinase (PI-3K) and mitogen-activated protein kinase (MAPK) pathways (Figure 1 G-I).
Conclusion: asTF is a more potent angiogenic factor than fl-TF via the non-hypoxic HIF-1α up-regulation through FAK-independent activation of MAPK and PI-3K pathways. This mechanism may contribute to the progression and complications of atherosclerosis.
- © 2013 by American Heart Association, Inc.