Distinct expression of three estrogen receptors in response to bisphenol A and nonylphenol in male Nile tilapias (Oreochromis niloticus)

Abstract

Environmental estrogens, such as bisphenol A (BisA) and nonylphenol (NP), have been shown to affect the estrogen receptor (ER) expression and induce male reproductive abnormalities. To elucidate molecular mechanisms of action of xenoestrogenic chemicals on the expression of estrogen receptors in the testes of Nile tilapia (Oreochromis niloticus), three full-length cDNAs respectively encoding ntERalpha, ntERbeta1 and ntERbeta2 were cloned from testes. The amino acid sequences of ntERalpha, ntERbeta1 and ntERbeta2 showed a high degree of similarity to the relevant fish species. Tissue-specific expression study showed that three receptors were highly expressed in pituitary, liver, testis, kidney and intestine tissues. The ntERalpha, ntERbeta1 and ntERbeta2 mRNA expressions were significantly higher at the sexual early recrudescing stage than at other recrudesced stages. After being exposed to xenoestrogens from weeks 2 to 4, the ntERalpha mRNA levels were increased significantly in testes after NP treatment at all sampling times or after 4 weeks of exposure to BPA. The ntERbeta1 mRNA levels remained unchanged, while a significant decrease of the ntERbeta2 mRNA level was observed in testes after exposure to NP and BPA. The present study demonstrates that the regulation of all three ntER subtypes in testes may act via different molecular mechanisms of exposure to NP and BPA.

Toxicity assessment and vitellogenin expression in zebrafish (Danio rerio) embryos and larvae acutely exposed to bisphenol A, endosulfan, heptachlor, methoxychlor and tetrabromobisphenol A

“…The induction of vtg1 appears to be controlled by the estrogen receptors after binding to the ligands and the chemicals tested. In a recent report on a study of estrogen receptor cDNA cloning and gene expression in male Nile tilapias, BPA was found to induce the expression of era mRNA, but not erb1 or erb2 mRNA (Huang et al, 2010). The molecular mechanisms of vtg1 induction by TBBPA and pesticides needs to be further examined to fully understand their levels of risk and toxicity.…”

The effects of phthalate and nonylphenol exposure on body size and secondary sexual characteristics during puberty

“…Lee et al (2013) showed that NP concentration in Taiwan river sediments was relatively higher than that in other countries (Fu et al, 2007;Lee et al, 2013;Li et al, 2004). NP is an estrogen mimic that can affect the endocrine system by disrupting signal pathways and by interacting with estrogen receptors (Huang et al, 2010;Laws et al, 2000).…”

Transcriptional activity and biological effects of mammalian estrogen receptor ligands on three hepatic estrogen receptors in Mozambique tilapia

“…This ER is a result of a duplication of the ER␤ gene; previously termed ER␣, ER␤, and ER␥, fish ERs were renamed ER␣, ER␤1, and ER␤2, respectively, to conform to zebrafish nomenclature [5,6]. Many tissues, of both male and female fish, co-express ER subtypes and levels can vary among tissues, genders, ontogeny, and reproductive and behavioral states [5,[7][8][9].…”