Development of ELISAs for the detection of vitellogenin in three marine fish from coastal areas of China

Establishment and application of multiple immunoassays for environmental estrogens based on recombinant Japanese flounder (Paralichthys olivaceus) choriogenin protein

Environmental estrogens have generated great concern because of their potential threat to aquatic organisms; however, the commonly used vitellogenin (Vtg) biomarker detection methods are not capable of detecting estrogenic activity below 10 ng/L 17β-estradiol. In this study, we developed multiple immunoassays based on Japanese flounder (Paralichthys olivaceus) choriogenin (Chg), a highly sensitive biomarker of environmental estrogens. Chg genes (ChgL and ChgH) of Japanese flounder were cloned for the first time, and a recombinant ChgL protein with a molecular weight of approximately 52 kDa was prepared using a prokaryotic expression system and purified using Ni-affinity column chromatography. Subsequently, specific monoclonal antibodies against ChgL were prepared and used to develop sandwich enzyme-linked immunosorbent assays (ELISAs), which had a detection range of 3.9-250 ng/mL and detection limit of 1.9 ng/mL. An immunofluorescence method was also established and used to visually detect ChgL induction in the tissues. In addition, a lateral flow immunoassay for ChgL that could detect estrogen activity within 10 min was developed. Finally, the reliability of the immunoassays was examined by measuring ChgL induction in the plasma and tissues of Japanese flounder exposed to 0, 2, 10, and 50 ng/L 17α-ethinylestradiol (EE₂). The results showed that 2 ng/L EE₂ notably increased ChgL levels in the plasma, demonstrating that ChgL is more sensitive than Vtg to environmental estrogens; 50 ng/L EE₂ induced obvious Chg induction in the sinusoidal vessels of the liver. Conclusions taken together, this study provides reliable methods for sensitive and rapid detection of estrogenic activity in aquatic environments.

Metamifop as an estrogen-like chemical affects the pituitary-hypothalamic-gonadal (HPG) axis of female rice field eels (Monopterus albus)

Metamifop (MET) is a widely used herbicide. It is likely for it to enter water environment when utilized, thus potential impacts may be produced on aquatic animals. Little information is available about its effects on the endocrine system of fish to date. In the current study, female rice field eels (Monopterus albus) were exposed to different MET concentrations (0, 0.2, 0.4, 0.6, 0.8 mg L -1) for 96 h to examine the effect of MET on the hypothalamic-pituitary-gonadal (HPG) axis and sexual reversal. The results showed that high concentrations of MET exposure increased vitellogenin (VTG) levels in liver and plasma, but plasma sex hormone levels were not affected by MET exposure. MET exposure increased the expression of CYP19A1b and CYP17 that regulate sex hormone production in the brain, but the expression of genes (CYP19A1a, CYP17, FSHR, LHCGR, hsd11b2, 3β-HSD) associated with sex hormone secretion in the ovary and the estrogen receptor genes (esr1, esr2a, esr2b) in the liver were all suppressed. In addition, the expression of sex-related gene (Dmrt1) was suppressed. This study revealed for the first time that MET has estrogen-like effects and has a strong interference with the expression of HPG axis genes. MET did not show the ability to promote the sexual reversal in M. albus, on the contrary, the genes expression showed that the occurrence of male pathway was inhibited.

Endocrine disruption in the sub Antarctic fish Patagonotothen tessellata (Perciformes, Notothenidae) from Beagle Channel associated to anthropogenic impact

Situated in the sub-Antarctic region, Beagle Channel represents a unique marine ecosystem due to the connection between the Pacific and the Atlantic Oceans, and its proximity to the Antarctic Peninsula. Ushuaia city, the biggest settlement on the channel, exerts an increasing anthropogenic pressure by discharges of urban and industrial effluents. In the present work, we use Patagonotothen tessellata, one of the most abundant and widespread species in the channel, as a bioindicator species in order to evidence anthropic impact from Ushuaia Bay and surrounding areas. We first analyzed and characterized real time gene expression of androgen receptor, estrogen receptor and different forms of vitellogenin (VTG), under laboratory conditions. This was achieved by induction with estradiol of P. tessellata males. Then, the selected genes were used as biomarkers for an environmental biomonitoring study. Morphometric indices and circulating sex steroids (estradiol and testosterone) were also quantified in male fish collected from different sites. The qPCR analysis showed that vtgAb form is more inducible than vtgAa or vtgC forms after estrogen induction. The field survey revealed the up-regulation of vtgAb and the androgen receptor in fish from sites with higher anthropogenic influence. Sex steroids followed seasonal variations according to their reproductive cycle, with higher levels of estradiol and testosterone in winter and summer seasons. The use of biomarkers such as gene expression of VTG demonstrates that fish from Ushuaia Bay are likely to be exposed to endocrine disrupting compounds. To our knowledge, this research is the first attempt to assess the endocrine disruption associated to anthropic impact in a widespread fish of the Beagle Channel and contributes to a better understanding of the reproductive physiology of sub Antarctic ichthyofauna.

Study of Heavy Metals Pollution and Vitellogenin Levels in Brown Trout (Salmo trutta trutta) Wild Fish Populations

The objectives of this research were, first, to determine the concentrations of certain heavy metals in the edible tissue of wild brown trout (Salmo trutta trutta) from two different rivers located in the Abruzzi region (Italy), and then, to investigate the levels of variation in vitellogenin (VTG) associated with the presence of metalloestrogens. VTG is an effective indicator for endocrine disturbance, and an increase in the vitellogenin levels in male fish is widely employed as a biomarker of estrogenic contamination in the aquatic environment. The muscles of the trout were analyzed for As, Cd, Co, Cr, Ni, Pb, Al, and Zn using an inductively coupled plasma-mass spectrometer (ICP-MS), and Hg was measured using a direct mercury analyzer (DMA-80). The calculated values of the condition factor confirmed a healthy status for this species, indicating that the aquatic habit in both rivers is suitable for brown trout life. No significant difference in the concentrations of each metal were reported between the trout from the two rivers, and no significant difference for VTG levels were found between male and female fish. It is interesting to note the high concentrations of Al/Zn, while the Pb, Cd, and Hg concentrations in all of the samples were lower than those established by the European Commission.

Screening of estrogenic endocrine-disrupting chemicals in meat products based on the detection of vitellogenin by enzyme-linked immunosorbent assay

Vitellogenin (VTG) is typically produced by females but when present in males can indicate contamination with estrogenic endocrine-disrupting chemicals (EDCs). Here we used primary hepatocytes isolated from male crucian carp uncontaminated with estrogenic EDCs as a culture model. Nine EDCs were used for validation, and an enzyme-linked immunosorbent assay (ELISA) was used to quantify VTG production by primary hepatocytes. The lower limit of detection of 17β-E2, DES, and HES using the method was 10^-12 M. Fresh pork was roasted, and non-hydrolytic acetonitrile-vortexing was used to extract potential estrogenic EDCs. The extracted substances were separated by thin-layer chromatography (TLC), and dimethyl terephthalate present in roast pork was found to induce high VTG concentrations. Therefore, the detection of VTG by ELISA provides a sensitive and reliable method for detecting known and unknown estrogenic EDCs in food products.

Impact of Endocrine Disruptors on Vitellogenin Concentrations in Wild Brown Trout (Salmo trutta trutta)

The adverse effects of endocrine disruptors (EDs) on aquatic wildlife and human health represent a current issue of high public concern. Substantial knowledge of the level of estrogenic EDs in fish has accumulated from field surveys. For this purpose, a survey of wild brown trout (Salmo trutta trutta) was carried out to assess the incidence of EDs in the feral fish population living in the Liri river (Abruzzi, Italy). The results of this study show that this aquatic environment possesses an estrogenic potency that triggered the increase of vitellogenin levels in both female and male trouts. Fish exposed to different pesticides and urban waste in downstream river showed higher vitellogenin levels in comparison to the headwater site. Furthermore, some trouts coming from the downstream reported the presence of several pesticides and fungicides, some of these banned several years ago.

Carbon nanotube-based DNA vaccine against koi herpesvirus given by intramuscular injection

Koi herpesvirus (KHV) also named Cyprinid Herpesvirus 3 (CyHV-3) is one of the most threatening pathogens affecting common carp production as well as the valued ornamental koi carp. The current commercial vaccines available are costly and potentially cause severe stress caused by live virus. KHV ORF149 gene has been proved encoding one of the main immunogenic proteins for KHV. In this study, we coupled a plasmid expression vector for ORF149 to single walled carbon nanotubes (SWCNTs) for an anti-KHV vaccine. The vaccine conferred an 81.9% protection against intraperitoneal challenge with KHV. Importantly, SWCNTs as a promising vehicle can enhanced the protective effects 33.9% over that of the naked DNA vaccine at the same dose. The protection was longer and serum antibody production, enzyme activities and immune-related gene expression were all induced in fish vaccinated with the nanotube-DNA vaccine compared with the DNA alone. Thereby, this study demonstrates that the ORF149 DNA vaccine loaded onto SWCNTs as a novel vaccine might provide an effective method of coping with KHV disease using intra-muscular vaccination.

Distribution of vitellogenin in Japanese flounder (Paralichthys olivaceus) for biomarker analysis of marine environmental estrogens

Estrogen pollution in marine environments has become a research hotspot due to its adverse effects on the reproduction of wild organisms. To early detection of estrogen pollution, this study developed two methods for detecting Japanese flounder vitellogenin (Vtg), a sensitive biomarker for environmental estrogens. Firstly, monoclonal antibodies (mAb) specific to Vtg were prepared using purified lipovitellin (Lv), a main Vtg-derived yolk protein. Anti-Lv mAb (C1F1) had the highest titer (1:256,000) and was labeled with fluorescein isothiocyanate to establish a direct immunofluorescence (DIF) method for histological detection of Vtg in tissues. Additionally, using the purified Lv and mAb, an enzyme-linked immunosorbent assay (ELISA) was developed and this assay had a detection limit of 0.75 ng/mL and a working range of 1.95-250 ng/mL. Furthermore, Vtg induction in the plasma of Japanese flounder exposed to 17β-estradiol (E₂), 17α-ethinylestradiol (EE₂), and bisphenol A (BPA) were quantified by ELISA, and Vtg induction in the liver of EE₂-exposed Japanese flounder were measured by DIF. Finally, the distribution of Vtg in Japanese flounder was detected using these two methods. The results revealed that Vtg mainly appeared in the terminal tail fin, liver, kidney, intestine, and spleen. Considering the high concentration of Vtg and easy sample collection, the terminal tail fin could be a new alternative to plasma for Vtg quantification, while kidney and liver are suitable for histological detection of Vtg.

Effects of pollution on marine organisms

This review covers selected 2018 articles on the biological effects of pollutants, including human physical disturbances, on marine and estuarine plants, animals, ecosystems, and habitats. The review, based largely on journal articles, covers field and laboratory measurement activities (bioaccumulation of contaminants, field assessment surveys, toxicity testing, and biomarkers) as well as pollution issues of current interest including endocrine disrupters, emerging contaminants, wastewater discharges, marine debris, dredging, and disposal. Special emphasis is placed on effects of oil spills and marine debris due largely to the 2010 Deepwater Horizon oil blowout in the Gulf of Mexico and proliferation of data on the assimilation and effects of marine debris. Several topical areas reviewed in the past (e.g., mass mortalities ocean acidification) were dropped this year. The focus of this review is on effects, not on pollutant sources, chemistry, fate, or transport. There is considerable overlap across subject areas (e.g., some bioaccumulation data may be appear in other topical categories such as effects of wastewater discharges, or biomarker studies appearing in oil toxicity literature). Therefore, we strongly urge readers to use keyword searching of the text and references to locate related but distributed information. Although nearly 400 papers are cited, these now represent a fraction of the literature on these subjects. Use this review mainly as a starting point. And please consult the original papers before citing them.

New methods for purification of Paralichthys olivaceus lipovitellin and immunoassay-based detection of vitellogenin

Increasing levels of estrogenic pollution in marine environments has made the development of reliable biological detection techniques urgently needed. In this study, Japanese flounder (Paralichthys olivaceus) lipovitellin (Lv) was purified and used to establish three immunological methods for the detection of vitellogenin (Vtg), a biomarker for environmental estrogens. Firstly, five different methods were employed to purify Lv, among which water-precipitation was the fastest and easiest way to purify Lv. Japanese flounder Lv was characterized as a phospholipoglycoprotein with a molecular weight of ∼369 kDa. Using purified Lv and its specific polyclonal antibody, a sandwich enzyme-linked immunosorbent assay (ELISA) was developed. This assay had a working range from 7.8 to 250 ng/mL and a detection limit of 3.1 ng/mL. Furthermore, we developed an immunohistochemistry (IHC) and an immunofluorescence (IF) assay, both of which allowed visual detection of liver Vtg. Finally, Vtg induction in plasma and liver of juvenile Japanese flounders exposed to 17β-ethinylestradiol (EE₂) was measured using these three methods. Exposure to 10 and 50 ng/L EE₂ significantly increased plasma Vtg levels, and obvious positive fluorescence signals were observed near the liver sinusoidal vessels. These results confirmed that the methods developed effectively detected estrogenic activity of exogenous chemicals. Therefore, this study provides reliable methodologies for biomonitoring of estrogenic pollution in marine environments.