ZFIN ID: ZDB-PUB-101108-16
AhR2-mediated, CYP1A-independent cardiovascular toxicity in zebrafish (Danio rerio) embryos exposed to retene
Scott, J.A., Incardona, J.P., Pelkki, K., Shepardson, S., and Hodson, P.V.
Date: 2011
Source: Aquatic toxicology (Amsterdam, Netherlands)   101(1): 165-174 (Journal)
Registered Authors: Incardona, John P.
Keywords: Alkylated polycyclic aromatic hydrocarbons, Retene, Aryl hydrocarbon receptor, Cytochrome P450 1A, Embryotoxicity, Cardiac development
MeSH Terms:
  • Analysis of Variance
  • Animals
  • Blood Flow Velocity/drug effects
  • Cardiovascular System/drug effects*
  • Cardiovascular System/metabolism
  • Cytochrome P-450 CYP1A1/metabolism
  • Edema, Cardiac/chemically induced*
  • Embryo, Nonmammalian/drug effects*
  • Embryo, Nonmammalian/metabolism
  • Enzyme Induction/drug effects
  • Gene Knockdown Techniques
  • Microscopy, Confocal
  • Oligonucleotides/genetics
  • Phenanthrenes/toxicity*
  • Receptors, Aryl Hydrocarbon/metabolism*
  • Zebrafish*
  • Zebrafish Proteins/metabolism*
PubMed: 21040984 Full text @ Aquat. Toxicol.
In the embryo-larval stages of fish, alkylphenanthrenes such as retene (7-isopropyl-1-methylphenanthrene) produce a suite of developmental abnormalities typical of exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), including pericardial and yolk sac edema, cardiovascular dysfunction, and skeletal deformities. To investigate the mechanism and target tissue of retene toxicity, we used observational, histological, and protein knockdown techniques in zebrafish (Danio rerio) embryos. The primary overt signs of toxicity are pericardial edema and reduced blood flow, first observed at 36h post-fertilization (hpf). The most pronounced effects at this stage are a reduced layer of cardiac jelly in the atrium and reduced diastolic filling. Conversely, an increased layer of cardiac jelly is observed at 72hpf in retene-exposed embryos. Induction of cytochrome P4501A (CYP1A) is apparent in a subset of cardiomyocytes by 48hpf suggesting that early cardiac effects may be due to AhR activation in the myocardium. Myocardial CYP1A induction is transient, with only endocardial induction observed at 72hpf. Knockdown of cyp1a by morpholino oligonucleotides does not affect retene toxicity; however, ahr2 knockdown prevents toxicity. Thus, the mechanism of retene cardiotoxicity is AhR2-mediated and CYP1A-independent, similar to TCDD; however, the onset and proximate signs of retene toxicity differ from those of TCDD. Retene cardiotoxicity also differs mechanistically from the cardiac effects of non-alkylated phenanthrane, illustrating that alkyl groups can alter toxic action. These findings have implications for understanding the toxicity of complex mixtures containing alkylated and non-alkylated polycyclic aromatic hydrocarbons.