Methyl tert butyl ether targets developing vasculature in zebrafish (Danio rerio) embryos

Abstract

Disruption of vascular endothelial growth factor (VEGF) signaling during early development results in abnormal angiogenesis and increased vascular lesions. Embryonic exposure to 0.625 to 10 mM methyl tert butyl ether (MTBE), a highly water soluble gasoline additive, resulted in a dose dependent increase in pooled blood in the common cardinal vein (CCV), cranial hemorrhages and abnormal intersegmental vessels (ISVs). The EC50s for the lesions ranked in terms of likelihood to occur with MTBE exposure were: pooled blood in the CCV, 3.2 mM [95 % CI: 2.2 – 4.7] > cranial hemorrhage, 11 mM [5.9 – 20.5] > abnormal ISV, 14.5 mM [6.5 – 32.4]. Organ systems other than the vascular system appear to develop normally, which suggests MTBE toxicity targets developing blood vessels. Equal molar concentrations (0.625 to 10 mM) of the primary metabolites, tertiary butyl alcohol (TBA) and formaldehyde, did not result in vascular lesions, which suggested that the parent compound is responsible for the toxicity. Stage specific exposures were carried out to determine the developmental period most sensitive to MTBE vascular disruption. Embryos treated until 6-somites or treated after Prim-5 stages did not exhibit a significant increase in lesions, while embryos treated between 6-somites and Prim-5 had a significant increase in vascular lesions (p ≤ 0.05). During the critical window for MTBE-induced vascular toxicity, expression of vegfa, vegfc, and flk1/kdr were significantly decreased 50, 70 and 40%, respectively. This is the first study to characterize disruption in vascular development following embryonic exposure to MTBE. The unique specificity of MTBE to disrupt angiogenesis may be mediated by the down regulation of critical genes in the VEGF pathway.

Craniofacial abnormalities and altered wnt and mmp mRNA expression in zebrafish embryos exposed to gasoline oxygenates ETBE and TAME

“…Husbandry (#03-014) and embryonic exposure protocols (#08-025) were approved by the Rutgers University Animal Care and Facilities Committee. During exposures, embryos were incubated at 25 °C as previously described, and all embryos were selected at the same stage at the beginning of each experiment (Bonventre et al 2011). …”

“…In order to directly compare these studies with the previously published MTBE zebrafish studies (Bonventre et al, 2011), embryos were exposed to 5 mM ETBE or TAME. Due to the lower LC50 for TAME, an additional concentration of 2.5 mM TAME was also used for the mRNA expression studies.…”

“…We previously reported MTBE induces vascular lesions in developing Danio rerio , including pooled blood in the common cardinal vein (CCV), cranial hemorrhages, and abnormal intersegmental vessels (ISV), while other tissues appear to develop normally (Bonventre et al, 2011). The vascular lesions occur following an exposure during the 6-somites to prim-25 stages of development, and are associated with a decrease in mRNA transcripts of vascular endothelial growth factor ( vegf ) - a and - c and vascular endothelial growth factor receptor 2 ( vegfr2 ) at the 21-somite stage.…”

Screening for angiogenic inhibitors in zebrafish to evaluate a predictive model for developmental vascular toxicity

“…Because vascular development is sensitive to drug or chemical perturbation [2; 3; 4] and is a potential mechanism of teratogenesis [5], screening for vascular toxicity provides information relevant to the developmental toxicity profile of environmental chemicals. Despite these observations, data concerning chemical-target interactions underlying developmental vascular toxicity is limited.…”

“…Despite these observations, data concerning chemical-target interactions underlying developmental vascular toxicity is limited. Previous studies have explored this issue utilizing experimental and computational models based on in vitro data from high-throughput screening (HTS) assays [2; 6; 7; 8; 9]. A multi-tiered approach, involving the integration of in vitro data with in silico models and in vivo apical endpoints is necessary to build insight into how chemical disruption of vascular development might ultimately lead to adverse outcomes.…”