Abstract
Genistein is a phytoestrogen found at a high level in soybeans. In vitro and in vivo studies showed that high concentrations of genistein caused toxic effects. This study was designed to test the feasibility of zebrafish embryos for evaluating developmental toxicity and estrogenic potential of high genistein concentrations. The zebrafish embryos at 24 h post-fertilization were exposed to genistein (1 3 10−4 M, 0.5 3 10−4 M, 0.25 3 10−4 M) or vehicle (ethanol, 0.1%) for 60 h. Genistein-treated embryos showed decreased heart rates, retarded hatching times, decreased body length, and increased mortality in a dose-dependent manner. After 0.25 3 10−4 M genistein treatment, malformations of survived embryos such as pericardial edema, yolk sac edema, and spinal kyphosis were also observed. TUNEL assay results showed apoptotic DNA fragments in brain. This study also confirmed the estrogenic potential of genistein by EGFP expression in the brain of the mosaic reporter zebrafish embryos. This study first demonstrated that high concentrations of genistein caused a teratogenic effect on zebrafish embryos and confirmed the estrogenic potential of genistein in mosaic reporter zebrafish embryos.
Highlights
Endocrine-active compounds (EACs) threaten ecosystems by disrupting normal endocrine function, which can lead to reproductive failure in humans and wildlife (Guillette et al 1994; Jobling et al 2002)
Developmental toxicity of genistein on zebrafish embryos Per-minute heart rates of genistein-treated embryos 30 h after treatment decreased in a dose-dependent manner (Fig. 1A)
About 90% of the 10 vehicle-treated embryos in each plate (8.83 ± 1.94 embryos) hatched 37 h after treatment; genistein treatment decreased the number of hatched embryos (0.25 3 10−4 M: 4.16 ± 1.47, 0.5 3 10−4 M: 1.16 ± 1.47 embryos)
Summary
Endocrine-active compounds (EACs) threaten ecosystems by disrupting normal endocrine function, which can lead to reproductive failure in humans and wildlife (Guillette et al 1994; Jobling et al 2002). EACs include synthetic estrogen, xeno-estrogen, and phytoestrogen. Phytoestrogens are a class of compounds found in a variety of plants (Legler et al 2000; Ingham et al 2004). Genistein (49,5,7-trihydroxyisoflavone) is a phytoestrogen found in high levels in soybeans (Messina et al 1994). High concentrations of genistein have been shown to cause apoptosis and necrosis in testis cells (Kumi-Diaka et al 1999), primary cortical neuron cultures from Spraugue-Dawley rats (Linford et al 2001), human thymocytes (McCabe and Orrenius 1993), and human lymphoblastoid cells (Morris et al 1998). In vivo studies showed that genistein causes developmental and growth toxicity, myelotoxicity, and brain apoptosis (Choi and Lee 2004; Ingham et al 2004; Guo et al 2005)
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