Transcriptional Response of Vitellogenin Gene in Flatfish to Environmental Pollutants from Two Regions of the Gulf of Mexico.

The present study evaluates the endocrine effect in flatfish through vitellogenin (vtg) gene expression and its association with pollutants data obtained from fish muscle and sediment from two regions in the Gulf of Mexico (GoM): Perdido Fold Belt (northwestern) and the Yucatan Peninsula (southeast). The results revealed induction of vtg in male flatfish in both geographical regions with different levels and patterns of distribution per oceanographic campaign (OC). In the Perdido Fold Belt, vtg was observed in male fish during four OC (carried out in 2016 and 2017), positively associated with Pb, V, Cd and bile metabolites (hydroxynaphthalene and hydroxyphenanthrene). In the Yucatan Peninsula, the induction of vtg in males was also detected in three OC (carried out in 2016 and 2018) mainly associated with Ni, Pb, Al, Cd, V and polycyclic aromatic hydrocarbons. Ultimately, estrogenic alterations could affect reproductive capacity of male flatfish in the GoM.

Acute Exposure to Crude Oil Induces Epigenetic, Transcriptional and Metabolic Changes in Juvenile Sciaenops ocellatus.

In this study, we report molecular and metabolic responses of Sciaenops ocellatus during an acute oil exposure bioassay (100, 800 and 8000 mg 1-1 of crude oil). The global DNA methylation and expression profiles of key genes of the xenobiotic biotransformation system (cytochrome P450 1A [cyp1a] and glutathione S-tranferase [gst]), oxidative stress system (glutathione peroxidase [gpx], catalase [cat], aldehyde dehydrogenase [aldh]) and reproductive system (vitellogenin [vtg]) were evaluated. At the metabolic level, we evaluated the concentration of four polycyclic aromatic hydrocarbon (PAH) metabolites -hydroxybenzo[a]pyrene, hydroxypyrene, hydroxynaphthalene and hydroxyphenanthrene- in fish bile. The results of this study revealed that fish exposed to crude oil exhibited hypomethylation of DNA, up-regulation of cyp1a and gst and down-regulation of gpx, cat, aldh and vtg and high concentrations of PAH metabolites with respect to the control.

The effect of benzo[a]pyrene on the gut microbiota of Nile tilapia (Oreochromis niloticus).

Benzo[a]pyrene (BaP) is a highly toxic and carcinogenic polycyclic aromatic hydrocarbon (PAH) whose toxicological effects in the gut microbiota of aquatic organisms have not yet been fully revealed. Therefore, in this study, we used high-throughput 16S rRNA gene sequencing to evaluate the effects of BaP in the gut microbiome of Oreochromis niloticus, including its possible participation in the process of detoxification and its ability to recover. The fish were injected with a single intraperitoneal dose of 20 mg kg-1 of BaP, and the effects in the microbiome were evaluated at 24, 72, and 120 h post-injection. The results indicate a clear dysbiosis (in composition, relative abundance, diversity, and interaction networks) of the gut microbiota during 24 h post-injection, dominated by Fusobacteria and Bacteroidetes and a decrease in Proteobacteria and Spirochaetae. Interestingly, a slight recovery of the microbiome begins at 72 h and stabilises at 120 h post-injection. Pathway analysis revealed the participation of the gut microbiome in PAH degradation mainly at 24 h post-injection. This study provides new insights in the toxicology of BaP in O. niloticus and the first evidence of the ability of the gut microbiome to recovery after a chemical disturbance. KEY POINTS: • Benzo[a]pyrene caused a dysbiosis in the gut microbiota of Oreochromis niloticus. • We observed an enrichment of bacteria involved in the metabolism of xenobiotics. • The gut microbiota was recovered after exposure to benzo[a]pyrene.

Gill and liver transcriptomic responses of Achirus lineatus (Neopterygii: Achiridae) exposed to water-accommodated fraction (WAF) of light crude oil reveal an onset of hypoxia-like condition.

Crude oil is one of the most widespread pollutants released into the marine environment, and native species have provided useful information about the effect of crude oil pollution in marine ecosystems. We consider that the lined sole Achirus lineatus can be a useful monitor of the effect of crude oil in the Gulf of Mexico (GoM) because this flounder species has a wide distribution along the GoM, and its response to oil components is relevant. The objective of this study was to compare the transcriptomic changes in liver and gill of adults lined sole fish (Achirus lineatus) exposed to a sublethal acute concentration of water-accommodated fraction (WAF) of light crude oil for 48 h. RNA-Seq was performed to assess the transcriptional changes in both organs. A total of 1073 differentially expressed genes (DEGs) were detected in gills; 662 (61.69%) were upregulated, and 411 (38.30%) were downregulated whereas in liver, 515 DEGs; 306 (59.42%) were upregulated, and 209 (40.58%) were downregulated. Xenobiotic metabolism and redox metabolism, along with DNA repair mechanisms, were activated. The induction of hypoxia-regulated genes and the generalized regulation of multiple signaling pathways support the hypothesis that WAF exposition causes a hypoxia-like condition.

Toxicity evaluation and microbiota response of the lined sole Achirus lineatus (Chordata: Achiridae) exposed to the light petroleum water-accommodated fraction (WAF).

Exposure to contaminants might directly affect organisms and alter their associated microbiota. The objective of the present study was to determine the impact of the petroleum-water-accommodated fraction (WAF) from a light crude oil (API gravity 35) on a benthic fish species native from the Gulf of Mexico (GoM). Ten adults of Achirus lineatus (Linnaeus, 1758) were exposed to a sublethal WAF/water solution of 50% v/v for 48 hr. Multiple endpoints were measured including tissue damage, presence of polycyclic aromatic hydrocarbons (PAHs) metabolites in bile and gut microbiota analyses. Atrophy and fatty degeneration were observed in livers. Nodules and inflammation were detected in spleen, and structural disintegration and atrophy in the kidney. In gills hyperplasia, aneurysm, and gills lamellar fusion were observed. PAHs metabolites concentrations in bile were significantly higher in exposed organisms. Gut microbiome taxonomic analysis showed significant shifts in bacterial structure and composition following WAF exposure. Data indicate that exposure to WAF produced toxic effects in adults of A. lineatus, as evidenced by histological alterations and dysbiosis, which might represent an impairment to long-term subsistence of exposed aquatic organisms.

Partial mRNA Sequences of the Biomarkers CYP1A, GST, CAT, GR, SOD, GPx, VTG and p53 in Flatfish Syacium gunteri from Gulf of Mexico.

The present study reports partial sequences of a group of genes used as exposure and effect biomarkers of organic contaminants and/or heavy metals in Syacium gunteri. In order to isolate these sequences, cDNA was used to amplify fragments between 200 and 800 bp, which were then cloned and sequenced. The sequences presented high percentages of identity with genes involved in the metabolism of xenobiotic biotransformation (cytochrome P4501A and glutathione S-transferase), oxidative stress (catalase, glutathione reductase, glutathione peroxidase and superoxide dismutase), reproductive system (vitellogenin) and with the tumor suppressor protein p53 reported in the GenBank database. Subsequently, from the deduced sequence of amino acids of each fragment, their tridimensional structure was predicted, using homologous proteins from the Protein Data Base. This study generates an important base of molecular biomarkers for the monitoring of environmental health in the Gulf of Mexico.