Gene expression analysis on growth, development and toxicity pathways of male Nile tilapia (Oreochromis niloticus), after acute and sub-chronic benzo (α) pyrene exposures.

Benzo[α]pyrene (BaP), a lipophilic polycyclic aromatic hydrocarbon (PAH), is a contaminant widely distributed in aquatic systems. Its presence in freshwater organisms is of great concern; particularly in Nile tilapia (Oreochromis niloticus), due to its economic relevance. The aim of this study is to evaluate the effects of acute and sub-chronic BaP exposures on molecular growth/development responses, toxicity to DNA pathways and xenobiotic metabolism. Negative morphometric changes (the growth condition factor, hepatosomatic and gonadosomatic indices), the fluorescent aromatic compounds (FACs) in bile were also studied in order to understand the mechanisms of action of BaP. Genes involved in the growth hormone GH/insulin-like growth factor 1 (IGF-1) were measured, such as IGF1-2 with the growth hormone receptor gene expression GHR1-2, and the endocrine disruption biomarker vitellogenin (VTG). Acute exposure elicited changes in the GH/IGF axis, mainly in the GHR1 and in IGF1 mRNA levels without affecting the GHR2 expression. While sub-chronic exposure had less effect on both GHR and IGF genes. The most notable tissue-specific effects and morphometric endpoints were observed upon sub-chronic exposure, such as changes in key genes involved in detoxification, DNA damage, and altered reproductive morphological endpoints; showing that sub-chronic BaP doses have longer-lasting toxic effects. This study shows that sub-chronic BaP exposure may compromise the health of Nile tilapia and sheds light on the changes of the GH/IGF axis and the biotransformation of the xenobiotics due to the presence of this contaminant.

Gene expression profile and molecular pathway datasets resulting from benzo(a)pyrene exposure in the liver and testis of adult tilapia.

Benzo(a)pyrene (BaP), the prototype of polycyclic aromatic hydrocarbons, is known to exhibits genotoxic and carcinogenic effects promoting molecular impacts. The dataset presented here is associated with the research article paper entitled "Transcriptome Analysis Reveals Novel Insights Into the Response of Low-dose Benzo(a)pyrene Exposure in Male Tilapia". In this article, we presented a transcriptomic characterization of male tilapia exposure to BaP in the short term. This data provides an extended analysis of changes in the gene expression and identification of pathways in the liver and testis of male tilapia exposure to BaP. We used gene set enrichment analysis (GSEA) and sub-network enrichment analysis (SNEA) to identify gene networks and pathways associated with molecular adverse effects of BaP exposure. The data indicates that target pathways related to promoting carcinogenesis such as DNA repair and DNA replication were affected as well as other crucial biological processes. Moreover, to determine whether some of the key reported genes of DNA damage are affected by BaP exposure, Quantitative PCR (qPCR) was performed. Gene set categories and sub-networks are provided and the corresponding signature differences from BaP exposure are listed. The information in these datasets may contribute to understanding the potential carcinogenesis mechanism of action from low BaP exposure.

Transcriptome analysis reveals novel insights into the response of low-dose benzo(a)pyrene exposure in male tilapia.

Despite a wide number of toxicological studies that describe benzo[a]pyrene (BaP) effects, the metabolic mechanisms that underlie these effects in fish are largely unknown. Of great concern is the presence of BaP in aquatic systems, especially those in close proximity to human activity leading to consumption of potentially contaminated foods. BaP is a known carcinogen and it has been reported to have adverse effects on the survival, development and reproduction of fish. The purpose of this study was to investigate if a low dose of BaP can alter genes and key metabolic pathways in the liver and testis in male adult tilapia, and whether these could be associated with biological endpoints disruption. We used both high-throughput RNA-Sequencing to assess whole genome gene expression following repeated intraperitoneal injections of 3 mg/kg of BaP (every 6 days for 26 days) and morphometric endpoints as indicators of general health. Condition factor (K) along with hepatosomatic and gonadosomatic indices (morphometric parameters) were significantly lower in BaP-treated fish than in controls. BaP exposure induced important changes in the gene expression pattern in liver and testis as revealed by both Pathway and Gene Ontology (GO) analyses. Alterations that were shared by both tissues included arachidonic acid metabolism, androgen receptor to prostate-specific antigen signaling, and insulin-associated effects on lipogenesis. The most salient liver-specific effects included: biological processes involved in detoxification, IL6-associated insulin resistance, mTOR hyperactivation, mitotic cytokinesis, spindle pole and microtubule binding. BaP effects that were confined to the testis included: immune system functions, inflammatory response, estrogen and androgen metabolic pathways. Taken together, gene expression and morphometric end point data indicate that the reproductive success of adult male tilapia could be compromised as a result of BaP exposure. These results constitute new insights on the mechanism of action of low dose BaP in a non-model organism (tilapia).