Effects of 2,5-hexanedione on angiogenesis and vasculogenesis in chick embryos

n-Hexane is widely used in industry and its metabolite, 2,5-hexanedione (2,5-HD), has been implicated as a neural toxin in the developing fetus. Using the chick embryo model, we have previously revealed the neurotoxicity of 2,5-HD during development and established that high dose of 2,5-HD was embryo lethal. In view of the close linkage in biology for neurogenesis and angiogenesis, we speculated that it was most likely caused by cardiovascular dysplasia, therefore in this study, we investigated the effects of 2,5-HD on the development of the vasculature, which involves vasculogenesis and angiogenesis. Using gastrulating chick embryos as a model, we demonstrated that the hemangioblasts (precursor of hematopoietic and endothelial cells) migrated to the area opaca where they form the blood islands. However, this process was impaired when the embryos were treated with 2,5-HD, suggesting that 2,5-HD is capable of impairing vasculogenesis. To study the effect of 2,5-HD exposure on angiogenesis, we used the chick yolk-sac membrane (YSM) and chorioallantoic membrane (CAM) models. We found that, at low (0.02 M) concentration, 2,5-HD stimulated angiogenesis while at higher concentrations (>0.1 M) it inhibited this process. This biphasic response of angiogenesis to 2,5-HD exposure was found to be associated with altered expression of the VEGF-R, FGF-2 and angiogenin. Moreover, we also determined that 2,5-HD exposure increased the reactive oxygen species (ROS) production. In conclusion, 2,5-HD could induce dysplasia in the developing vasculature, which in turn could cause extravascular hemolysis and the embryos to die.