Abstract
Purpose :
Echinomycin (EKN), an inhibitor of hypoxia-inducible factor (HIF)-1 DNA-binding activity, has been implied as a possible therapeutic agent in ischemic diseases. Here, we assess EKN in hypoxia-driven responses in vitro using human primary adult retinal pigment epithelium cells (aRPE), and in vivo using the laser-induced mouse choroidal neovascularization (CNV) model.
Methods :
aRPE were kept at normoxia (20% O2) or exposed to hypoxia (1% O2), in the presence or absence of EKN. Epithelial wound-healing was used to determine the dose of EKN for our experiments. Effects of EKN on hypoxia-mediated pathways were analyzed by western blot for HIF-1a protein, quantitative PCR of HIF-target genes, and proteome array for soluble angiogenic factors. Inhibition of angiogenesis by EKN was determined in human primary adult retinal endothelial cells (aREC), exposed to EKN-treated hypoxic conditioned aRPE medium by spheroid sprouting assay. 8-week-old C57BL/6J mice underwent laser-induced CNV, as a model of HIF-associated ocular neovascularization. Animals were treated on days 3 and 6 post-laser with recombinant mouse VEGFR1-Fc chimera protein (mouse equivalent of aflibercept) or EKN, and compared to vehicle-treated controls. CNV lesion area was determined on day 9, by fluorescein angiography.
Results :
aRPE-19 treated with 5pM of EKN showed hypoxia-dependent significantly decreased cell proliferation in the wound-healing assay. A lower protein expression of HIF-1a concomitant with lower HIF-mediated transcripts were detected in hypoxic aRPE cells treated with EKN compared with non-treated controls, under hypoxic conditions. These results were confirmed by proteome profiler for angiogenic factors, and subsequent reduced hREC sprouting. Laser-induced mice treated with 1 mg of intravitreally injected EKN showed significantly decreased vascular lesion area when compared with 1 mg of VEGFR1 chimera or vehicle-treated controls.
Conclusions :
Our data suggest EKN as a potent inhibitor of HIF-mediated angiogenesis in retinal cells and in the mouse model of CNV, which could have future implications in the treatment of patients with nAMD.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.