Histological and Histochemical Evaluation of the Effects of Graphene Oxide on Thyroid Follicles and Gas Gland of Japanese Medaka (Oryzias latipes) Larvae

A systematic review of the evaluation of endocrine-disrupting chemicals in the Japanese medaka (Oryzias latipes) fish

Japanese medaka (Oryzias latipes) is an acceptable small laboratory fish model for the evaluation and assessment of endocrine-disrupting chemicals (EDCs) found in the environment. In this research, we used this fish as a potential tool for the identification of EDCs that have a significant impact on human health. We conducted an electronic search in PubMed (http://www.ncbi.nlm.nih.gov/pubmed) and Google Scholar (https://scholar.google.com/) using the search terms, Japanese medaka, Oryzias latipes, and endocrine disruptions, and sorted 205 articles consisting of 128 chemicals that showed potential effects on estrogen-androgen-thyroid-steroidogenesis (EATS) pathways of Japanese medaka. From these chemicals, 14 compounds, namely, 17β-estradiol (E2), ethinylestradiol (EE2), tamoxifen (TAM), 11-ketotestosterone (11-KT), 17β-trenbolone (TRB), flutamide (FLU), vinclozolin (VIN), triiodothyronine (T3), perfluorooctanoic acid (PFOA), tetrabromobisphenol A (TBBPA), terephthalic acid (TPA), trifloxystrobin (TRF), ketoconazole (KTC), and prochloraz (PCZ), were selected as references and used for the identification of apical endpoints within the EATS modalities. Among these endpoints, during classification, priorities are given to sex reversal (masculinization of females and feminization of males), gonad histology (testis-ova or ovotestis), secondary sex characteristics (anal fin papillae of males), plasma and liver vitellogenin (VTG) contents in males, swim bladder inflation during larval development, hepatic vitellogenin (vtg) and choriogenin (chg) genes in the liver of males, and several genes, including estrogen-androgen-thyroid receptors in the hypothalamus-pituitary-gonad/thyroid axis (HPG/T). After reviewing 205 articles, we identified 108 (52.68%), 46 (22.43%), 19 (9.26%), 22 (17.18%), and 26 (12.68%) papers that represented studies on estrogen endocrine disruptors (EEDs), androgen endocrine disruptors (AEDs), thyroid endocrine disruptors (TEDs), and/or steroidogenesis modulators (MOS), respectively. Most importantly, among 128 EDCs, 32 (25%), 22 (17.18%), 15 (11.8%), and 14 (10.93%) chemicals were classified as EEDs, AEDs, TEDs, and MOS, respectively. We also identified 43 (33.59%) chemicals as high-priority candidates for tier 2 tests, and 13 chemicals (10.15%) show enough potential to be considered EDCs without any further tier-based studies. Although our literature search was unable to identify the EATS targets of 45 chemicals (35%) studied in 60 (29.26%) of the 205 articles, our approach has sufficient potential to further move the laboratory-based research data on Japanese medaka for applications in regulatory risk assessments in humans.

Evaluation of pancreatic δ- cells as a potential target site of graphene oxide toxicity in Japanese medaka (Oryzias latipes) fish

In continuation to our previous investigations on graphene oxide (GO) as an endocrine disrupting chemical (EDC), in the present experiment, we have investigated endocrine pancreas of Japanese medaka adults focusing on δ-cells in the islet organs as an endpoint. Breeding pairs of adult male and female fish were exposed to 0 mg/L (control) or 20 mg/L GO by continuous immersion (IMR) for 96 h, or to 0 µg/g or 100 µg/g GO by a single intraperitoneal (IP) administration and depurated 21 days in a GO-free environment. Histological investigations indicated that the endocrine cells are concentrated in one large principal islet, and several small secondary islets scattered within the mesentery near the liver and intestine. The cells of the islet organ are in various shapes with basophilic nuclei and eosinophilic cytoplasm. Immunohistochemical evaluation using rabbit polyclonal antisomatostatin antibody indicated that immunoreactivity is localized either at the periphery or at the central region in principal islets, and throughout the secondary islets, and found to be enhanced in fish exposed to GO than controls. The soma of δ-cells exhibits neuron-like morphology and have filopodia like processes. Cell sorting as non-communicating δ-cells (NCDC), communicating cells (CC), and non- δ-cells (NDC) indicated that within an islet organ, the population of NDCC is found to be the least and NDC is the highest. Our data further indicated that GO-induced impairments in the islet organs of medaka pancreas are inconsistent and could be affected by the exposure roots as well as the sex of the fish.

Per- and polyfluoroalkyl substances activate UPR pathway, induce steatosis and fibrosis in liver cells

Per- and polyfluoroalkyl substances (PFAS), which include perfluorooctanoic acid (PFOA), heptafluorobutyric acid (HFBA), and perfluorotetradecanoic acid (PFTA), are commonly occurring organic pollutants. Exposure to PFAS affects the immune system, thyroid and kidney function, lipid metabolism, and insulin signaling and is also involved in the development of fatty liver disease and cancer. The molecular mechanisms by which PFAS cause fatty liver disease are not understood in detail. In the current study, we investigated the effect of low physiologically relevant concentrations of PFOA, HFBA, and PFTA on cell survival, steatosis, and fibrogenic signaling in liver cell models. Exposure of PFOA and HFBA (10 to 1000 nM) specifically promoted cell survival in HepaRG and HepG2 cells. PFAS increased the expression of TNFα and IL6 inflammatory markers, increased endogenous reactive oxygen species (ROS) production, and activated unfolded protein response (UPR). Furthermore, PFAS enhanced cell steatosis and fibrosis in HepaRG and HepG2 cells which were accompanied by upregulation of steatosis (SCD1, ACC, SRBP1, and FASN), and fibrosis (TIMP2, p21, TGFβ) biomarkers expression, respectively. RNA-seq data suggested that chronic exposures to PFOA modulated the expression of fatty acid/lipid metabolic genes that are involved in the development of NFALD and fatty liver disease. Collectively our data suggest that acute/chronic physiologically relevant concentrations of PFAS enhance liver cell steatosis and fibrosis by the activation of the UPR pathway and by modulation of NFALD-related gene expression.

Histopathological evaluation of the interrenal gland (adrenal homolog) of Japanese medaka (Oryzias latipes) exposed to graphene oxide

Due to unique physicochemical properties and wide industrial and biomedical applications, graphene oxide (GO) is ubiquitous in the aquatic ecosystem. Using Japanese medaka (Oryzias latipes) fish as a model, we previously demonstrated minimal endocrine disrupting (ED) effects of GO on reproductive organs, and thyroids. Current study investigated the ED-effects of GO on the interrenal gland (IRG) of medaka. Breeding pairs of adult male and female fish were exposed to 0 mg/L (control) or 20 mg/L GO by continuous immersion for 96 h, or to 0 or 100 μg/g GO by intraperitoneal administration. Also, 1 day post-hatch (dph) larvae were exposed to different concentrations of GO (2.5-20 mg/L) for 96 h. IRG was evaluated by immunohistochemical techniques after 21 days depuration in adults and 6 weeks in larvae. IRG cells were counted and the nuclear area was measured in hematoxylin-eosin stained sections using ImageJ software. We found that IRG is distributed adjacent to the posterior cardinal vein and its branches within the head kidney. Columnar/oval shaped periodic acid-Schiff negative, tyrosine hydroxylase positive cells are arranged either in a single, or in groups, sometimes encircling a sinusoid, or in a straight chord, laying adjacent to the endothelium of the cardinal vein, and having eosinophilic cytoplasm with round/oval basophilic nuclei. GO effect on nuclei and cell population in IRG was inconsistent; depending on exposure route, sex, and/or age of the fish. Also, because of its high adsorptive property and sharp edges, GO probably agglomerated on IRG, and induced physical injury, and ED effects.

Impacts of ingested MWCNT-Embedded nanocomposites in Japanese medaka (Oryzias latipes)

Polymer nanocomposites combine the versatile, lightweight characteristics of polymers with the properties of nanomaterials. Polyethylene terephthalate glycol (PETG) is commonly used in polymer additive manufacturing due to its controllable transparency, high modulus, and mechanical properties. Multi-walled carbon nanotubes (MWCNTs) add tensile strength, electrical conductivity, and thermal stability. The increased use of nanocomposites has led to concern over potential human health risks. We assessed morphologic alterations to determine impacts of ingested abraded nanocomposites compared to its component materials, pristine MWCNTs (1000 mg/L) and PETG. Adult transparent Japanese medaka (Oryzias latipes) were administered materials via oral gavage in 7 doses over 16 days. In vivo observations revealed altered livers and gallbladders following exposure to pristine MWCNTs and nanocomposites. Subsequent histologic sections showed fish exposed to pristine MWCNTs had highly altered biliary structures, and exposure to nanocomposites resulted in hepatocellular alteration. Thyroid follicle proliferation was also observed in fish exposed to materials containing MWCNTs. Transmission electron microscopy of livers showed that hepatocytes of fish exposed to MWCNTs had widespread swelling of rough endoplasmic reticulum, pronounced lysosomal activity, and swelling of intrahepatic biliary passageways. Fish exposed to nanocomposites had areas of degenerated hepatocytes with interspersed cellular debris. Each analysis showed that fish exposed to pristine PETG were most similar to controls. These results suggest that MWCNTs are the source of toxicity in abraded nanocomposite materials but that nanocomposites may also have some unique effects. The similarities of many teleost and mammalian tissues are such that these findings may indicate human health risks.

Preparation of beta-cyclodextrin based nanocomposite for magnetic solid-phase extraction of organic ultraviolet filters

A simple and efficient analytical method for organic UV filters (UV-Fs) in environmental samples has been established in this study. Taking advantage of the hydrophobicity on the inner cavity, hydrophilicity on the outer wall, and host-guest interaction provided by beta-cyclodextrin, a core-shell magnetic extraction material was firstly synthesized by using a facile method. The extractant was utilized in magnetic solid-phase extraction of UV-Fs in complex environmental samples, including beach sand, sediment and river water samples, followed by the quantitation using high-performance liquid chromatography. A series of factors affecting extraction efficiencies of seven UV-Fs were profoundly optimized. Under the optimal conditions, the linear ranges were at 5.0-5.0 × 10² ng mL^-1 for the UV-Fs with regression coefficients (r) at 0.9984-0.9998. The limits of detection were from 0.12 to 1.4 ng mL^-1. The recoveries were in the range of 84.2-109%. Furthermore, the molecular dynamics simulations and independent gradient model analysis were applied to reveal the adsorption configuration and interaction mechanisms between target analytes and the sorbent.

Experimental data sets on the evaluation of graphene oxide as a thyroid endocrine disruptor and a modulator of gas gland cells in Japanese medaka (Oryzias latipes) larvae at the onset of maturity

This article presents the experimental datasets obtained from the histological/histochemical studies of endocrine disrupting effects of graphene oxide (GO) on thyroid follicles and gas gland (GG) cells of Japanese medaka larvae at the onset of maturity. The experiment was conducted on one day-post hatch (dph) starved fries (orange-red variety) immersed in different concentrations of GO (2.5-20.0 mg/L) and no GO (controls) in embryo-rearing medium (ERM) for 96 h under laboratory conditions (25 ± 1 °C; light cycle 16 h light: 8 h dark). After treatment, larvae were maintained in balanced salt solution (BSS) with food and allowed depuration for 6 more weeks in a GO-free environment. On 47 dph, the larvae were anesthetized in MS 222 and their total lengths (mm) and weights (mg) were measured, and they were then cut into three small pieces (head, trunk, and tail). Head and trunk regions were fixed in 4% PFA in 20 mM PBS for 48 h at room temperature and the post-anal tail was preserved in TRI reagent and kept at −20 °C until analysis. Tissues in 4% PFA were used for cutting 5µm thick paraffin sections in a manual rotary microtome. Sections of head regions were evaluated for thyroid follicles after hematoxylin-eosin (HE) or Periodic acid-Schiff (PAS) staining. Trunk sections were used for swim bladder (SB) inflation studies and for phenotypic sex (ovary and testis) of the larvae after HE staining. Genetic sex assessment was made from tail DNA by genotyping Y chromosome-specific male sex-determining gene dmy. Digital images were captured by using either an Olympus B-max 40 microscope attached to a camera with Q-capture Pro 7 software or an Olympus CKX53 microscope with DP22 camera and CellSens software. Images of thyroid follicles and GG cells were analyzed using imagej software. HE stained histological sections of thyroid follicles near the heart and branchial regions were captured and the area (µm²) of individual follicles (minimum 3) available in the entire section were measured. The heights of thyrocytes (µm) were determined directly. Manual counting of GG cells was made from the digital images captured in several regions of the SB avoiding blood cells and other cells which have indistinct nucleus and pale cytoplasm; results were expressed as the number of GG cells/mm². Data were analyzed by GraphPad prism version 7.04. For normally distributed data, one-way ANOVA followed by post-hoc Tukey's test or unpaired parametric “t” test including Welch's correction was used. Otherwise, Kruskal-Wallis test followed by nonparametric Mann-Whitney's test as a post hoc test was used. Data were expressed as means ±SEM and the level of significance was set at p < 0.05.