Abstract
Chemical compounds produced by humans are continuously reaching the environment. In this work, we characterised the expression patterns of important endocrine-related genes involved in the ecdysone pathway in the fourth larval instar of the model species Chironomus riparius after exposure to three chemicals: ethinyl oestradiol (EE), nonylphenol (NP) and bis(tributyltin) oxide (TBTO). We used real-time PCR to analyse the gene expression levels of ecdysone receptor (EcR) and ultraspiracle (usp), two genes that encode the dimerising partners of the functional ecdysone receptor; the orphan receptor ERR (oestrogen-related receptor), with an unknown function in invertebrates; and E74, an early response gene induced by ecdysteroids. We estimated the bioaccumulation potential, bioavailability and physicochemical properties of these chemicals, together with a number of other exogenous agents known to interfere with the hormonal system. We also provide a review of previous transcriptional studies showing the effect of all these chemicals on ecdysone cascade genes. This analysis provides useful data for future ecotoxicological studies involving invertebrate species.CapsuleChanges in transcriptional activities of EcR, E74, usp and ERR genes after exposure to endocrine-disrupting chemicals would be useful as molecular bioindicators of endocrine disruption in Chironomus riparius.
Highlights
Endocrine-disrupting chemicals (EDCs) are substances that alter a wide variety of physiological, biochemical and/or molecular processes in an organism by interfering with the regulatory networks of endogenous hormones
We compared between the control and the treated larvae using analysis of variance (ANOVA) with Dunnett’s multiple comparison tests
We examined the effects of 24 h and 96 h ethinyl oestradiol (EE), NP and TBTO exposure on ecdysone receptor (EcR) expression in C. riparius fourth instar larvae using real-time PCR; 24 h exposure to 5 mg/L EE and 96 h exposure to 0.5 mg/L EE increased EcR mRNA levels (Fig. 1A)
Summary
Endocrine-disrupting chemicals (EDCs) are substances that alter a wide variety of physiological, biochemical and/or molecular processes in an organism by interfering with the regulatory networks of endogenous hormones. Toxicity testing provides information about the physiological effects of toxicants, but there is still a gap with regard to the mechanisms of action of the toxicant and the response of the organism at the cellular and molecular levels. In this sense, the Environ Sci Pollut Res changes in transcriptional activities of several selected genes after exposure to EDCs have proven to be a very useful tool as molecular bioindicators of endocrine disruption in aquatic invertebrates (Kim et al, 2015; Poynton and Vulpe, 2009). Myriad studies have been performed to distinguish the effects of different environmental pollutants on the expression of genes of interest in this insect (Aquilino et al, 2016; Herrero et al, 2017, 2018; Martínez-Paz et al, 2012, 2017; Morales et al, 2013, 2014, 2020; Nair and Choi, 2012; Nair et al, 2013; Ozáez et al, 2013, 2014; Park and Kwak, 2010; Planelló et al, 2007, 2008, 2010, 2011, 2015)
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