Environmental Pollutants Impair Transcriptional Regulation of the Vitellogenin Gene in the Burrowing Mud Crab (Macrophthalmus Japonicus)

Effects of di-(2-ethylhexyl) terephthalate on hypothalamus-pituitary-gonad axis in adult zebrafish

Di-(2-ethylhexyl) terephthalate (DEHTP) is frequently used in food packaging and medical devices as an alternative to di-(2-ethylhexyl) phthalate (DEHP). In this study, zebrafish pairs were exposed to DEHTP for 21 d and the effects on fertility, sex hormone levels, vitellogenin levels, and transcription of genes along the hypothalamic-pituitary-gonad axis were evaluated. Results showed that mean egg numbers were significantly reduced in the 30 and 300 μg/L DEHTP groups. The adverse effects of DEHTP on hormones and gene transcripts were more prominent in males than in females. In male fish, the gonadosomatic index, hepatosomatic index, and vitellogenin concentration were significantly increased. The results of a significant decrease in testosterone (T) and an increase in the 17β-estradiol (E2)/T ratio in males exposed to 3-300 μg/L DEHTP suggest that the endocrine potential of DEHTP is similar that of DEHP. In females, genes related to gonadotropin-releasing hormone and gonadotropin were up-regulated while E2 was significantly down-regulated. These findings suggest that positive E2 feedback mechanisms in the hypothalamus and pituitary gland are activated to balance sex hormones. The effects of chronic exposure to DEHTP on the neuroendocrine system require further investigation.

Antibodies targeting the European lobster (Palinurus elephas) vitellogenin developed by mRNA isolation and in-silico-designed antigenic peptides

Vitellogenin is an essential protein involved in ovary maturation in many animals. Detection of this protein correlated with reproductive capacity may be important if carried out on marine organisms such as the red spiny lobster Palinurus elephas, a crustacean that is an economically important crop from wild fish catches. Moreover, in recent years, vitellogenin has assumed an important role as a possible biomarker of marine environmental pollution, as its expression levels can be influenced by the presence of similar estrogen pollutants and can affect the reproductive sphere of marine organisms such as crustaceans. The P. elephas vitellogenin protein and its coding gene have never been isolated, so there is little information about its presence in this lobster. The aim of the present study was to develop a molecular strategy to create, for the first time, an antibody for the detection and quantization of vitellogenin in P. elephas.

Summary: The development of anti-vitellogenin antibodies of Palinurus elephas could be applied to building a non-invasive reading system for monitoring the reproductive status of these crustaceans and as a useful tool for controlling the quality of their aquatic environment.

Reference gene and tropomyosin expression in mud crab Scylla olivacea, Scylla paramamosain and Scylla tranquebarica

Tropomyosin, a muscle tissue protein is a major allergen in most of shellfish including mud crab. Quantitative real time-PCR (qRT-PCR) using a stable reference gene is the most sensitive approach to produce accurate relative gene expression that has yet to be demonstrated for allergenic tropomyosin in mud crab species. This study was conducted to identify the suitable reference gene and tropomyosin expression in different body parts of local mud crabs, Scylla olivacea, Scylla paramamosain and Scylla tranquebarica. Myosin, 18S rRNA, GADPH and EF1α were selected as candidate reference genes and their expression was measured in the abdomen, walking leg and cheliped tissues of local Scylla spp. The expression stability was analyzed using the comparative delta-Ct method, BestKeeper, NormFinder and geNorm then comprehensively ranked by RefFinder algorithm. Findings showed that EF1α was the most suitable reference gene across three mud crab species. Meanwhile, the abdomen, walking leg and cheliped selected their own suitable reference gene either Myosin, 18S rRNA, EF1α or GADPH. Overall, tropomyosin was the highest in S. tranquebarica, whereas the least was in S. paramamosain. Interestingly, tropomyosin was the highest in the abdomen of all mud crab species. This is the first analysis on reference genes selection for qRT-PCR data normalization of tropomyosin expression in mud crab. These results will provide more accurate findings for further gene expression and allergen analysis in Scylla spp.

In vitro effects of selected endocrine disruptors (DEHP, PCB118, BPA) on narrow-clawed crayfish (Astacus leptodactylus) primary cells

Environmental pollutants with endocrine-disrupting effect are of global importance due to their contribution to the aethiologies of variety of complex diseases. These lipophilic pollutants are persistent in the environment and able to bioaccummulate in nontarget organisms. BPA, DEHP and PCB118 (dioxin-like PCB) are associated with endocrine disruption effects, while information on their effects on aquatic invertebrates are limited. In the current study, the effects of these compounds, which are ubiqutous and present at low concentrations in the environment, are studied in the primary hepatopancreas, muscle, gill, intestine and gonadal cultures of narrow-clawed crayfish (Astacus leptodactylus Eschscholtz, 1823), a widely distributed freshwater crayfish in Turkey with high economic importance. IC50 values following MTT assay ranged 0.27-12.61 nM; when compared with other tissues, the gonads were more affected with lower IC50 values. PCB118 induced higher cytotoxicity, while DEHP was the least toxic compound. This is the first study on the primary culture of A. leptodactylus¸ and the toxic effects of these compounds in this organism providing mechanistic insights on the responses and detoxification capacity of the organs. This study provides basis to unravel the mechanism of action of the tested EDCs in crayfish and improvement of cell culture conditions for ecotoxicity and screening assays.

Expression Levels of the Immune-Related p38 Mitogen-Activated Protein Kinase Transcript in Response to Environmental Pollutants on Macrophthalmus japonicus Crab

Environmental pollution in the aquatic environment poses a threat to the immune system of benthic organisms. The Macrophthalmus japonicus crab, which inhabits tidal flat sediments, is a marine invertebrate that provides nutrient and organic matter cycling as a means of purification. Here, we characterized the M. japonicus p38 mitogen-activated protein kinase (MAPK) gene, which plays key roles in the regulation of cellular immune and apoptosis responses. M. japonicusp38 MAPK displayed the characteristics of the conserved MAPK family with Thr-Gly-Tyr (TGY) motif and substrate-binding site Ala-Thr-Arg-Trp (ATRW). The amino acid sequence of the M. japonicus p38 MAPK showed a close phylogenetic relationship to Eriocheir sinensis MAPK14 and Scylla paramamosainp38 MAPK. The phylogenetic tree displayed two origins of p38 MAPK: crustacean and insect. The tissue distribution patterns showed the highest expression in the gills and hepatopancreas of M. japonicus crab. In addition, p38 MAPK expression in M. japonicus gills and hepatopancreas was evaluated after exposure to environmental pollutants such as perfluorooctane sulfonate (PFOS), irgarol, di(2-ethylhexyl) phthalate (DEHP), and bisphenol A (BPA). In the gills, p38 MAPK expression significantly increased after exposure to all concentrations of the chemicals on day 7. However, on day 1, there were increased p38 MAPK responses observed after PFOS and irgarol exposure, whereas decreased p38 MAPK responses were observed after DEHP and BPA exposure. The upregulation of p38 MAPK gene also significantly led to M. japonicus hepatopancreas being undertested in all environmental pollutants. The findings in this study supported that anti-stress responses against exposure to environmental pollutants were reflected in changes in expression levels in M. japonicusp38 MAPK signaling regulation as a cellular defense mechanism.

Effects of di-(2-ethylhexyl) phthalate on Transcriptional Expression of Cellular Protection-Related HSP60 and HSP67B2 Genes in the Mud Crab Macrophthalmus japonicus

Di-2-ethylhexyl phthalate (DEHP) has attracted attention as an emerging dominant phthalate contaminant in marine sediments. Macrophthalmus japonicus, an intertidal mud crab, is capable of tolerating variations in water temperature and sudden exposure to toxic substances. To evaluate the potential effects of DEHP toxicity on cellular protection, we characterized the partial open reading frames of the stress-related heat shock protein 60 (HSP60) and small heat shock protein 67B2 (HSP67B2) genes of M. japonicus and further investigated the molecular effects on their expression levels after exposure to DEHP. Putative HSP60 and small HSP67B2 proteins had conserved HSP-family protein sequences with different C-terminus motifs. Phylogenetic analysis indicated that M. japonicus HSP60 (Mj-HSP60) and M. Japonicus HSP67B2 (Mj-HSP67B2) clustered closely with Eriocheir sinensis HSP60 and Penaeus vannamei HSP67B2, respectively. The tissue distribution of Heat shock proteins (HSPs) was the highest in the gonad for Mj-HSP60 and in the hepatopancreas for Mj-HSP67B2. The expression of Mj-HSP60 Messenger Ribonucleic Acid (mRNA) increased significantly at day 1 after exposure to all doses of DEHP, and then decreased in a dose-dependent and exposure time-dependent manner in the gills and hepatopancreas. Mj-HSP67B2 transcripts were significantly upregulated in both tissues at all doses of DEHP and at all exposure times. These results suggest that cellular immune protection could be disrupted by DEHP toxicity through transcriptional changes to HSPs in crustaceans. Small and large HSPs might be differentially involved in responses against environmental stressors and in detoxification in M. japonicus crabs.