Title: Manipulation of the HIF-Vegf pathway rescues methyl tert-butyl ether (MTBE)-induced vascular lesions.

Authors: Bonventre, Josephine A; Kung, Tiffany S; White, Lori A; Cooper, Keith R

Published In Toxicol Appl Pharmacol, (2013 Dec 15)

Abstract: Methyl tert-butyl ether (MTBE) has been shown to be specifically anti-angiogenic in piscine and mammalian model systems at concentrations that appear non-toxic in other organ systems. The mechanism by which MTBE targets developing vascular structures is unknown. A global transcriptome analysis of zebrafish embryos developmentally exposed to 0.00625-5mM MTBE suggested that hypoxia inducible factor (HIF)-regulated pathways were affected. HIF-driven angiogenesis via vascular endothelial growth factor (vegf) is essential to the developing vasculature of an embryo. Three rescue studies were designed to rescue MTBE-induced vascular lesions: pooled blood in the common cardinal vein (CCV), cranial hemorrhages (CH), and abnormal intersegmental vessels (ISV), and test the hypothesis that MTBE toxicity was HIF-Vegf dependent. First, zebrafish vegf-a over-expression via plasmid injection, resulted in significantly fewer CH and ISV lesions, 46 and 35% respectively, in embryos exposed to 10mM MTBE. Then HIF degradation was inhibited in two ways. Chemical rescue by N-oxaloylglycine significantly reduced CCV and CH lesions by 30 and 32% in 10mM exposed embryos, and ISV lesions were reduced 24% in 5mM exposed zebrafish. Finally, a morpholino designed to knock-down ubiquitin associated von Hippel-Lindau protein, significantly reduced CCV lesions by 35% in 10mM exposed embryos. In addition, expression of some angiogenesis related genes altered by MTBE exposure were rescued. These studies demonstrated that MTBE vascular toxicity is mediated by a down regulation of HIF-Vegf driven angiogenesis. The selective toxicity of MTBE toward developing vasculature makes it a potentially useful chemical in the designing of new drugs or in elucidating roles for specific angiogenic proteins in future studies of vascular development.

PubMed ID: 24128854

MeSH Terms: Animals; Cell Line, Tumor; Down-Regulation; Hypoxia-Inducible Factor 1/genetics; Hypoxia-Inducible Factor 1/metabolism*; Methyl Ethers/toxicity*; Neovascularization, Physiologic/drug effects; RNA, Messenger/genetics; RNA, Messenger/metabolism; Signal Transduction; Transcriptome; Vascular Diseases/chemically induced; Vascular Diseases/drug therapy*; Vascular Diseases/genetics; Vascular Endothelial Growth Factor A/genetics; Vascular Endothelial Growth Factor A/metabolism*; Von Hippel-Lindau Tumor Suppressor Protein/genetics; Von Hippel-Lindau Tumor Suppressor Protein/metabolism; Zebrafish Proteins/genetics; Zebrafish Proteins/metabolism*; Zebrafish/embryology