Molecular cloning and characterization of an estrogen receptor gene in the marine polychaete Perinereis aibuhitensis

Mechanisms of intestinal injury in polychaete Perinereis aibuhitensis caused by low-concentration fluorene pollution: Microbiome and metabonomic analyses

The polychaete Perinereis aibuhitensis is used for bioremediation; however, its ability to remove fluorene, a common environmental pollutant, from sediments remains unclear, especially at low concentrations of fluorene (10 mg/kg). In this study, we explored the mechanism of intestinal injury induced by low concentrations of fluorene and the reason intestinal injury is alleviated in high fluorene concentration groups (100 and 1000 mg/kg) using histology, ecological biomarkers, gut microbiome, and metabolic response analyses. The results show that P. aibuhitensis showed high tolerance to fluorene in sediments, with clearance rates ranging 25-50 %. However, the remediation effect at low fluorene concentrations (10 mg/kg) was poor. This is attributed to promoting the growth of harmful microorganisms such as Microvirga, which can cause metabolic disorders, intestinal flora imbalances, and the generation of harmful substances such as 2-hydroxyfluorene. These can result in severe intestinal injury in P. aibuhitensis, reducing its fluorene clearance rate. However, high fluorene concentrations (100 and 1000 mg/kg) may promote the growth of beneficial microorganisms such as Faecalibacterium, which can replace the dominant harmful microorganisms and improve metabolism to reverse the intestinal injury caused by low fluorene concentrations, ultimately restoring the fluorene-removal ability of P. aibuhitensis. This study demonstrates an effective method for evaluating the potential ecological risks of fluorene pollution in marine sediments and provides guidance for using P. aibuhitensis for remediation.

Is there potential for estradiol receptor signaling in lophotrochozoans?

Estrogen receptors (ERs) are thought to be the ancestor of all steroid receptors and are present in most lophotrochozoans studied to date, including molluscs, annelids, and rotifers. A number of studies have investigated the functional role of estrogen receptors in invertebrate species, although most are in molluscs, where the receptor is constitutively active. In vitro experiments provided evidence for ligand-activated estrogen receptors in annelids, raising important questions about the role of estrogen signalling in lophotrochozoan lineages. Here, we review the concordant and discordant evidence of estradiol receptor signalling in lophotrochozoans, with a focus on annelids and rotifers. We explore the de novo synthesis of estrogens, the evolution and expression of estrogen receptors, and physiological responses to activation of estrogen receptors in the lophotrochozoan phyla Annelida and Rotifera. Key data are missing to determine if de novo biosynthesis of estradiol in non-molluscan lophotrochozoans is likely. For example, an ortholog for the CYP11 gene is present, but confirmation of substrate conversion and measured tissue products is lacking. Orthologs CYP17 and CYP19 are lacking, yet intermediates or products (e.g. estradiol) in tissues have been measured. Estrogen receptors are present in multiple species, and for a limited number, in vitro data show agonist binding of estradiol and/or transcriptional activation. The expression patterns of the lophotrochozoan ERs suggest developmental, reproductive, and digestive roles but are highly species dependent. E2 exposures suggest that lophotrochozoan ERs may play a role in reproduction, but no strong dose-response relationship has been established. Therefore, we expect most lophotrochozoan species, outside of perhaps platyhelminths, to have an ER but their physiological role remains elusive. Mining genomes for orthologs gene families responsible for steroidogenesis, coupled with in vitro and in vivo studies of the steroid pathway are needed to better assess whether lophotrochozoans are capable of estradiol biosynthesis. One major challenge is that much of the data are divided across a diversity of species. We propose that the polychaetes Capitella teleta or Platyneris dumerilii, and rotifer Brachionus manjavacas may be strong species choices for studies of estrogen receptor signalling, because of available genomic data, established laboratory culture techniques, and gene knockout potential.

Expression Profile of Hydroxysteroid Dehydrogenase-like 2 in Polychaete Perinereis aibuhitensis in Response to BPA

Hydroxysteroid dehydrogenases (HSDs) play an important role in the metabolism of steroids and xenobiotics. However, the function of HSDs in invertebrates is unclear. In this study, we cloned the hydroxysteroid dehydrogenase-like 2 (HSDL2) gene in Perinereis aibuhitensis, which is 1652 bp in length, encoding 400 amino acids. This sequence contains conserved short-chain dehydrogenase and sterol carrier protein-2 domain, and the alignment analysis showed its close relationship with other invertebrate HSDL2. Further, the tissue distribution analysis of the HSDL2 gene showed it is expressed strongly in the intestine. The expression level of HSDL2 after inducement with bisphenol A (BPA) was also detected both at transcriptional and translational levels. The results inferred that BPA exposure can induce HSDL2 expression, and the inductive effect was obvious in the high-concentration BPA group (100 μg/L). In summary, our results showed the detoxification function of HSDL2 in polychaetes.

Identification of a novel CYP4V gene in the polychaete Perinereis aibuhitensis: transcriptional comparison with a CYP4B gene exposed to PAHs

Polychaete worms can biotransform polycyclic aromatic hydrocarbons (PAHs) in environments, and the cytochrome P450 (CYP) enzyme plays an important role in this process. Herein, a novel cytochrome P450 gene was identified and characterized from the polychaete worm Perinereis aibuhitensis. The full-length cDNA, which is named CYP4V82, is 1709 bp encoding a protein of 509 amino acids and has high similarity to CYP4V. The expression levels of CYP4V82 and CYP4BB4 (a CYP gene identified from P. aibuhitensis in a previous study, Chen et al. Mar Pollut Bull 64:1782-1788, 2012) exposure to various concentrations of benzo[a]pyrene (B[a]P) (0.5, 2, 4, and 8 μg/L) and same mass concentrations of fluoranthene (Flu, 3.2 μg/L), phenanthrene (Phe, 2.9 μg/L), B[a]P (4.0 μg/L) were detected to identify the function of the CYP4 family in P. aibuhitensis. Compared with CYP4BB4, CYP4V82 mRNA was minimally expressed on day 7 but highly sensitive on day 14. Notably, the expression levels of CYP4V82 and CYP4BB4 were relatively different in short-term responses to PAHs with different benzene rings of the same concentration. The expression of CYP4V82 in the B[a]P group was the highest, while that of CYP4BB4 in the Phe group was relatively higher than the two other groups. These findings suggest that PAHs are associated with the induction of CYP4V82 and CYP4BB4 expressions in P. aibuhitensis, which may have different efficiencies in the detoxification of PAHs.

Expression variations of two retinoid signaling pathway receptors in the rotifer Brachionus calyciflorus exposed to three endocrine disruptors

Endocrine disruption compounds (EDC) are known to affect reproduction, development, and growth of exposed organisms. Although in vertebrates, EDCs mainly act through steroid receptors (e.g. androgen and estrogen receptors), their absence in many invertebrates suggests the involvement of another biological pathway in endocrine disruption effects. As retinoid signaling pathway is present in almost all Metazoa and its involvement in the endocrine disruption of gastropods (i.e. imposex) has been demonstrated, the present work was devoted to investigating the relative mRNA variations of two retinoid receptors genes, retinoid X receptor (RXR) and retinoid acid receptor (RAR), in the freshwater rotifer Brachionus calyciflorus exposed for 6, 12 and 24 h to flutamide, fenitrothion and cyproterone acetate, three anti-androgens known to disrupt sexual reproduction of Brachionus sp. Results revealed that fenitrothion did not affect the relative mRNA levels RXR and RAR in B. calyciflorus, whereas RXR and RAR mRNA levels could be significantly increased by 2 to 4.5-fold and from 2 to 7-fold after exposure to flutamide and cyproterone acetate, respectively. Moreover, the effects of flutamide and cyproterone acetate were measured from 6 and 12 h of exposure, respectively. Cyproterone acetate caused the highest increase of RXR and RAR mRNA levels, probably due to its progestin activity in addition to its anti-androgenic activity and the potential presence of a membrane-associated progesterone receptor as reported in Brachionus manjavacas. Consequently, although it is still difficult to evaluate the hormonal pathways involved in the endocrine disruption in Brachionus sp., this work suggests that the retinoid signaling pathway appears to be a good starting point to try to elucidate the molecular mechanisms involved in sexual reproductive dysfunction in Brachionidae.

Invertebrates facing environmental contamination by endocrine disruptors: Novel evidences and recent insights

The crisis of biodiversity we currently experience raises the question of the impact of anthropogenic chemicals on wild life health. Endocrine disruptors are notably incriminated because of their possible effects on development and reproduction, including at very low doses. As commonly recorded in the field, the burden they impose on wild species also concerns invertebrates, with possible specificities linked with the specific physiology of these animals. A better understanding of chemically-mediated endocrine disruption in these species has clearly gained from knowledge accumulated on vertebrate models. But the molecular pathways specific to invertebrates also need to be reckoned, which implies dedicated research efforts to decipher their basic functioning in order to be able to assess its possible disruption. The recent rising of omics technologies opens the way to an intensification of these efforts on both aspects, even in species almost uninvestigated so far.

Impacts of in vivo and in vitro exposures to tamoxifen: Comparative effects on human cells and marine organisms

Tamoxifen (TAM) is a first generation-SERM administered for hormone receptor-positive (HER+) breast cancer in both pre- and post-menopausal patients and may undergo metabolic activation in organisms that share similar receptors and thus face comparable mechanisms of response. The present study aimed to assess whether environmental trace concentrations of TAM are bioavailable to the filter feeder M. galloprovincialis (100 ng L^-1) and to the deposit feeder N. diversicolor (0.5, 10, 25 and 100 ng L^-1) after 14 days of exposure. Behavioural impairment (burrowing kinetic), neurotoxicity (AChE activity), endocrine disruption by alkali-labile phosphate (ALP) content, oxidative stress (SOD, CAT, GPXs activities), biotransformation (GST activity), oxidative damage (LPO) and genotoxicity (DNA damage) were assessed. Moreover, this study also pertained to compare TAM cytotoxicity effects to mussels and targeted human (i.e. immortalized retinal pigment epithelium - RPE; and human transformed endothelial cells - HeLa) cell lines, in a range of concentrations from 0.5 ng L^-1 to 50 μg L^-1. In polychaetes N. diversicolor, TAM exerted remarkable oxidative stress and damage at the lowest concentration (0.5 ng L^-1), whereas significant genotoxicity was reported at the highest exposure level (100 ng L^-1). In mussels M. galloprovincialis, 100 ng L^-1 TAM caused endocrine disruption in males, neurotoxicity, and an induction in GST activity and LPO byproducts in gills, corroborating in genotoxicity over the exposure days. Although cytotoxicity assays conducted with mussel haemocytes following in vivo exposure was not effective, in vitro exposure showed to be a feasible alternative, with comparable sensitivity to human cell line (HeLa).

Freshwater snail Parafossarulus striatulus estrogen receptor: Characteristics and expression profiles under lab and field exposure

The modes of action by which putative endocrine disrupting chemicals (EDCs) elicit toxicity in mollusks remains unclear due to our limited understanding of the molluscan endocrine system. We identified and partially characterised the estrogen receptor (ER) of the mollusk Parafossarulus striatulus. The full-length cDNA of the ER of P. striatulus (psER) was isolated and found to have an ORF of 1386 bp which corresponded to 461 amino acids. Phylogenetic analysis revealed that psER is an orthologue of ER of other mollusks. Moreover, the DNA-binding domain, ligand-binding domain, P-box, D-box, and AF2 domain were also identified in psER. Exposure of females and males to 17β-estradiol (E2, 100 ng/L) for 24 h and 72 h did not alter psER transcription, but exposure to 17α-methyltestosterone (MT, 100 μg/L) for 72 h significantly decreased ER transcription in females only (p < 0.05). psER transcription was surveyed in males and females seeded in different regions in Taihu Lake, China. psER transcription were elevated among females and males maintained at site ML. This elevation was statistically significant (p < 0.05) among male snails as compared to snails held at the more pristine site of SZ. This was different to the results from lab, implying that some unknown chemicals or other environmental factors in field could affect psER transcription level in snails. Furthermore, females and males held at site ML also exhibited a significant elevation in vitellogenin transcription as compared to snails held at site SZ, suggesting that vitellogenin production may be directly regulated by psER or co-regulated with psER in this species.