Variation of the genetic expression pattern after exposure to estradiol-17β and 4-nonylphenol in male zebrafish (Danio rerio)

There is much concern about the increasing presence in the environment of synthetic chemicals that are able to disrupt the endocrine system. Among these compounds, 4-nonylphenol (4-NP) is one of the most studied xenoestrogens, due to its widespread accumulation in water sediment and consequent presence in fatty acid of aquatic organisms. Here, we have used a zebrafish microarray representing 16,399 genes to study the effects of 4-NP and estradiol-17b (E2) in adult male zebrafish in order to elucidate the mechanism of action of 4-NP compared with that of E2. The microarray results showed that both 4-NP and E2 induced a strong expression of vitellogenin (VTG), the sex related precursor of the yolk proteins in oviparous vertebrates. Both treatments induced elevated protein turnover upregulating genes involved in proteolysis and those that are constituents of the ribosome. Many genes regulated by 4-NP and E2 are involved in energy metabolism, oxidative stress defense mechanisms, xenobiotic metabolism, and lipid metabolism. A different pattern of expression in the two treatments was found for genes involved in oxidative stress, since E2 seems to induce the mechanism of detoxification, while 4-NP seems to inhibit this protective mechanism of the cell. Overall, these findings demonstrate that the microarray approach can contribute significantly to the understanding of expression patterns induced by E2 and 4-NP in male zebrafish. The results also demonstrate that 4-NP is able to act through an alternative pattern to that of estradiol-17b, modulating the expression of the same genes in a different manner.