Transcription Factor Ets-1 Mediates Ischemia- and Vascular Endothelial Growth Factor-Dependent Retinal Neovascularization

Abstract

Transcription factor Ets-1 has been reported to regulate angiogenesis in vascular endothelial cells. Here, we investigated a mechanism that may regulate the expression of Ets-1 in vascular endothelial growth factor (VEGF)- and hypoxia-induced retinal neovascularization and that may have potential to inhibit ocular neovascular diseases. VEGF and hypoxia increased Ets-1 expression in cultured bovine retinal endothelial cells. The VEGF-induced mRNA increase of Ets-1 was suppressed by a tyrosine kinase inhibitor (genistein), by inhibitors of MEK (mitogen-activated protein and extracellular signal-regulated kinase kinase) (PD98059 and UO126), and by inhibitors of protein kinase C (GF109203X, staurosporine, and Gö6976). Dominant-negative Ets-1 inhibited VEGF-induced cell proliferation, tube formation, and the expression of neuropilin-1 and angiopoietin-2. In a mouse model of proliferative retinopathy, Ets-1 mRNA was up-regulated. Intravitreal injection of dominant-negative Ets-1 suppressed retinal angiogenesis in a mouse model of proliferative retinopathy. In conclusion, VEGF induces Ets-1 expression in bovine retinal endothelial cells and its expression is protein kinase C/ERK pathway-dependent. Ets-1 up-regulation is involved in the development of retinal neovascularization, and inhibition of Ets-1 may be beneficial in the treatment of ischemic ocular diseases.

CCL2 Regulates Angiogenesis via Activation of Ets-1 Transcription Factor

“…In addition, a study by Watanabe et al (47) on retinal endothelial cells showed that VEGF and hypoxia-induced Ets-1 mRNA expression and that this was diminished after MEK/ERK1/2 blockade. That study indicated two very important points: 1) MEK/ERK1/2 induced phosphorylation of Ets-1 and enhanced its DNA-binding activity to certain genes; and 2) phosphorylated Ets-1 could bind to its own promoter and regulate its own presence and activity in cells via this feedback mechanism (47). These increases in Ets-1 mRNA level were considered to be associated with the transformation of brain endothelial cells into the angiogenic phenotype.…”

“…Thus, hepatocyte growth factor/scatter factor induces scattering and morphogenesis of epithelial cells through phosphorylation and activation of Ets-1 as the result of MAPK pathway activation (53,54). In addition, a study by Watanabe et al (47) on retinal endothelial cells showed that VEGF and hypoxia-induced Ets-1 mRNA expression and that this was diminished after MEK/ERK1/2 blockade. That study indicated two very important points: 1) MEK/ERK1/2 induced phosphorylation of Ets-1 and enhanced its DNA-binding activity to certain genes; and 2) phosphorylated Ets-1 could bind to its own promoter and regulate its own presence and activity in cells via this feedback mechanism (47).…”

SP100 inhibits ETS1 activity in primary endothelial cells

“…It is well documented that the expression level of ETS1 protein in endothelial cells is increased following the addition of growth factors and cytokines that positively contribute to angiogenesis, such as VEGF (Iwasaka et al, 1996;Watanabe et al, 2004) and TNF-a (Goetze et al, 2001). However, the potential modulation of SP100 protein in response to these factors has not been examined.…”

“…VEGF increased the level of ETS1 protein over time, but did not significantly affect SP100 or DAXX expression (Figure 1c). ETS1 protein has been shown to increase in response to hypoxic conditions Watanabe et al, 2004), so the modulation of SP100 protein expression using the hypoxia mimetic CoCl 2 was also tested. While ETS1 protein levels increased in response to CoCl 2 , no significant increase in SP100 or DAXX protein expression was observed (Figure 1d).…”

“…It has been subsequently demonstrated that ETS1 expression is induced by a wide spectrum of bioactive molecules including nitric oxide (Shimizu et al, 2004), H 2 O 2 (Yasuda et al, 1999), angiogenic growth factors such as vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF) (Iwasaka et al, 1996), tumor necrosis factor-a (TNF-a) (Goetze et al, 2001) and HGF (Tomita et al, 2003), as well as hypoxia Watanabe et al, 2004). Consistent with its induction by angiogenic factors, much evidence has been gathered demonstrating the functional role of ETS1 in the facilitation and progression of angiogenesis.…”