Angiogenesis results in the formation of new blood vessels. Tumor growth, tissue wound and inflammation can induce angiogenesis. Rapid tumor cell growth creates intracellular hypoxia, which initiates a series of cell signaling events that promote angiogenesis. Hypoxia-inducible factor (HIF) is a transcription factor that responds to changing intracellular oxygen concentration. Under typical oxygen levels (normoxia), HIF is hydroxylated and acetylated, modifications that target the transcription factor for VHL mediated ubiquitin degradation. During hypoxia, HIF accumulates and is transported to the nucleus where it induces expression of a wide variety of target gene products, including proteins important for inducing tumor endothelial cell angiogenesis. Growth factors (such as VEGF, FGF, and TGF) induce signaling pathways (including PLCγ, PI3K, Src, Smad signaling) that result in endothelial cell proliferation, increase vascular permeability and cell migration. Extracellular matrix proteases and regulators induce tissue matrix remodeling in preparation for migration of endothelial cells from existing vessels to form new tubing. Cytokines promote additional tumor growth and induce the expression of signaling proteins (i.e. Slit2) that promote the creation of tumor-associated blood vessels. In addition to hypoxia, PI3K and Ras pathways can increase HIF expression by promoting HIF translation. Tissue wounding, ischemia or inflammation recruit macrophage and bone marrow-derived inflammatory cells (BDMC) to wound areas, where these monocytes induce a similar panel of secreted proteins to induce angiogenesis.
eNOS SignalingMolecular mechanisms involved in the regulation of the endothelial nitric oxide synthase
Flow-dependent regulation of endothelial nitric oxide synthase: role of protein kinases
Caveolin regulation of endothelial function
Nitric oxide inhibition of adenylyl cyclase type 6 activity is dependent upon lipid rafts and caveolin signaling complexes
Nitric oxide production in the sphenoidal sinus by the inducible and constitutive isozymes of nitric oxide synthase
High glucose-induced apoptosis in human vascular endothelial cells is mediated through NF-kappaB and c-Jun NH2-terminal kinase pathway and prevented by PI3K/Akt/eNOS pathway