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

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 0.00625–5 mM MTBE suggested 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 knockdown 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.

The Transcriptome of the Zebrafish Embryo After Chemical Exposure: A Meta-Analysis

“…Since studies are based on different motivations and assumptions, the experimental strategies also differed with respect to exposure concentrations. Five of 33 studies used an exposure concentration showing no phenotypic effects in the embryo (e.g., Bonventre et al , 2013 ; Driessen et al , 2015 ; Hao et al , 2013 ), 3 studies used the lowest concentration leading to a sublethal phenotypic or lethal effect (e.g., Saili et al , 2013 ) and 8 studies used concentrations causing death of 5–20% of all embryos (e.g., Klüver et al , 2011 ; Lam et al , 2011 ; Oliveira et al , 2013 ). Five studies recorded phenotypic effects for the applied exposure concentrations but did not quantify the effects (e.g., Alexeyenko et al , 2010 ; White et al , 2011 ; Tal et al , 2012 ).…”

“…Additionally, experiments using no-effect concentrations showed fewer significantly regulated genes than experiments using a concentration reported to cause visible effects on the phenotype ( Figure 3d ). The fact that some contrasts do not show any significantly regulated genes goes in hand with the published studies about the corresponding datasets, since some of these studies chose not to correct their statistical test for multiple hypothesis testing for deriving a list of regulated genes ( Bonventre et al, 2013 ; Garcia-Reyero et al , 2014 ; Saili et al , 2013 ; Xu et al , 2014 ). Other studies tested a range of concentrations with the lower concentrations not always causing significant transcriptional changes.…”

A genomics-based framework for identifying biomarkers of human neurodevelopmental toxicity

“…We obtained whole embryo rat [23] and zebrafish datasets [48] (Supplemental Table 1). As described above, datasets were processed, annotated, and merged with the NDB set (and related human data) using the OGS identifier.…”

Exploring the HIFs, buts and maybes of hypoxia signalling in disease: lessons from zebrafish models

“…Using bright fluorescent transgenic lines that mark vessel endothelia [e.g. the Tg(fli:GFP) transgenic line], it has been shown that the potentially clinically relevant anti-angiogenic properties of methyl tert -butyl ether, with a previously unknown mechanism of action, are a result of the downregulation of Hif- and Vegf-dependent angiogenesis ( Bonventre et al, 2013 ). More recently, the direct HIF-VEGF link has been investigated and applied to other disease situations that are not traditionally associated with angiogenesis.…”