Effects of the lipid regulating drug clofibric acid on PPARα-regulated gene transcript levels in common carp (Cyprinus carpio) at pharmacological and environmental exposure levels

Hepatic transcriptome profiling of largemouth bass (Micropterus salmoides Lacépède) injected with Flavobacterium covae or lipopolysaccharide

Flavobacterium covae (columnaris) is the most detrimental bacterial disease affecting the largemouth bass (Micropterus salmoides Lacépède) aquaculture industry. In the current study, fish received an intraperitoneal injection of either 1× PBS (100 μL), LPS in PBS (100 μL, 10 μg/mL), or F. covae (100 μL, 2.85 × 1011 CFU/mL) to simulate immunological challenges. After 24 h post-injection, liver tissue from the control and treated groups were then collected for transcriptome analysis. Results of the Gene Ontology (GO) and KEGG pathway analyses for the F. covae and LPS-injected groups found differentially expressed genes (DEGs) enriched primarily in toll-like receptors (TLRs), cytokine-cytokine receptors, complement and coagulation cascades, and the PPAR signalling pathways. This suggests that the liver immune system is enhanced by these five combined pathways. Additionally, the DEGs TLR5, MYD88, and IL-1 were significantly upregulated in F. covae and LPS-injected fish compared to the controls, whereas IL-8 was downregulated. The upregulation of TLR5 was unexpected as F. covae lacks flagellin, the protein that binds to TLR5. Additionally, it is unknown whether the TLR5 is upregulated by LPS. Further research into the upregulation of TLR5 is warranted. These results provide insight into immune responses and associated pathways contributing to the immune system in the liver during columnaris infection and induced response to LPS in largemouth bass.

Fish as models to study liver and blood lipid-related effects of fibrates and statins and screen new hypolipidemic drugs

Fibrates and statins lead worldwide prescriptions of lipid-lowering drugs, whose consumption is increasing considerably due to the growing incidence of dyslipidemias, particularly in high-income areas. Consequently, these chemicals are frequently found in aquatic environments, usually closer to highly urbanized and populated areas, reaching the water systems primarily through waste-water treatment plant (WWTP) effluents. Despite that, the knowledge regarding the effects caused by fibrates and statins in fish, namely in liver lipid metabolism and blood-related parameters, is still very limited. There is yet no standardized fish model for testing the effects of those drugs. However, experimental evidence suggests that the mechanisms of action (MoA) of fibrates and statins are fairly similar to those observed in humans, which makes these aquatic organisms viable alternatives for toxicological and mechanistic studies. This graphical review serves as a state point regarding the potential use of fish as a model for the study of hypolipidemic compounds, addressing (I) the current state of aquatic pollution caused by statins and fibrates, (II) the experimental designs used in the literature to assess effects on fish, (III) the liver metabolism and blood effects caused by exposure to fibrates and statins, as well as (IV) the MoA of both drugs. It further focuses on the current and future benefits of establishing a standardized fish model(s) for testing hypolipidemic drugs.

Toxic effects of tire wear particles and the leachate on the Chinese mitten crab (Eriocheir sinensis)

Tire wear particles (TWPs) were considered as an important component of microplastic pollution in the aquatic environment. To understand the ecotoxicity of TWPs to crustacean, this study investigated toxic effects of TWPs and the leachate on the mitten crab Eriocheir sinensis and the accumulation of TWPs in the crabs. Although TWPs could be accumulated in various tissues (i.e., liver, gills and gut) of the crabs, exposure to TWPs or the leachate had no lethal effect on the crabs in this study. Lower concentrations of TWPs and the leachate exposure could stimulate the antioxidant defense system of the crabs, while higher concentrations could disrupt the stress defense system. In addition, the energy supply and metabolism of the crabs could also be affected by TWPs or the leachate. The transcriptomic profiles showed that the toxic mechanisms of TWPs and the leachate were not exactly the same. Similar to the results of biochemical analysis, several Gene Ontology (GO) terms and the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to oxidative stress and energy metabolism were significantly regulated by both TWPs and the leachate. However, TWPs could affect the expression of genes enriched in immune-related pathways, while the leachate regulated the enrichment of some other signaling pathways including FoxO signaling pathway, insulin signaling pathway, RIG-I-like receptor signaling pathway, NOD-like receptor signaling pathway, PPAR signaling pathway and neuroactive ligand-receptor interaction. Overall, our study could provide basic biological information for assessing the ecological risk of the TWP pollution in the aquatic environment and was useful to understand the potential toxic mechanisms of the TWPs and the leachate to crustaceans.

Effects of Stocking Density on the Growth Performance, Physiological Parameters, Antioxidant Status and Lipid Metabolism of Pelteobagrus fulvidraco in the Integrated Rice-Fish Farming System

Pelteobagrus fulvidraco is a freshwater fish commonly raised in rice fields, yet the optimal stocking density for this species remains unknown. Therefore, this study aimed to investigate the appropriate stocking density of P. fulvidraco in integrated rice-fish farming systems. Three different stocking densities--low density (LD, 125 g/m2), middle density (MD, 187.5 g/m2), and high density (HD, 250 g/m2)--were set up to evaluate P. fulvidraco's growth performance, stress indices, immune function, antioxidant status, and lipid metabolism after 90 days of farming. The results indicated that HD treatment had a detrimental effect on P. fulvidraco's growth parameters. HD treatment led to an increase in cortisol (Cor) and lactate (La) levels, but a decrease in glucose (Glu) content in serum. After 90 days of farming, an immune response accompanied by the increase of complement 3 (C3), C4, and immunoglobulin M (IgM) was observed in the HD group. Meanwhile, HD treatment induced oxidative stress and altered antioxidative status evidenced by the levels of catalase (CAT), glutathione peroxidase (Gpx), glutathione (GSH), malondialdehyde (MDA), superoxide dismutase (SOD), and total antioxidant capacity (T-AOC) in serum or liver. Additionally, the lipid metabolism-related genes including lipoprotein lipase (lpl), peroxisome proliferators-activated receptor (pparα), carnitine palmitoyltransferase-1 (cpt-1), and sterol regulatory element binding protein-1 (srebp-1) were markedly downregulated in the HD and/or MD group after 90 days of farming. In conclusion, this study contributes to a better understanding of P. fulvidraco's response to different stocking densities in integrated rice-fish farming systems. We suggest that the appropriate stocking density for P. fulvidraco in these farming systems should be below 250 g/m2, considering both fish growth and physiological responses.

Elucidating the Effects of the Lipids Regulators Fibrates and Statins on the Health Status of Finfish Species: A Review

The most documented fibrates are gemfibrozil, clofibrate and bezafibrate, while for statins, the majority of the published literature focuses on atorvastatin and simvastatin. The present work reviews previously published research concerning the effects of these hypocholesterolaemic pharmaceuticals on fish, with a particular focus on commercially important species, commonly produced by the European aquaculture industry, specifically in recirculated aquaculture systems (RAS). Overall, results suggest that both acute and chronic exposures to lipid-lowering compounds may have adverse effects on fish, disrupting their capacity to excrete exogenous substances, as well as both lipid metabolism and homeostasis, causing severe ontogenetic and endocrinological abnormalities, leading to hampered reproductive success (e.g., gametogenesis, fecundity), and skeletal or muscular malformations, having serious repercussions on fish health and welfare. Nonetheless, the available literature focusing on the effects of statins or fibrates on commonly farmed fish is still limited, and further research is required to understand the implications of this matter on aquaculture production, global food security and, ultimately, human health.

Effect of Siberian Ginseng Water Extract as a Dietary Additive on Growth Performance, Blood Biochemical Indexes, Lipid Metabolism, and Expression of PPARs Pathway-Related Genes in Genetically Improved Farmed Tilapia (Oreochromis niloticus)

Overnutrition in high-density aquaculture can negatively affect the health of farmed fish. The Chinese herbal medicine Siberian ginseng (Acanthopanax senticosus, AS) can promote animal growth and immunity, and regulate lipid metabolism. Therefore, we conducted an 8-week experiment, in which Oreochromis niloticus was fed with a diet supplemented with different concentrations of AS water extract (ASW) (0‰, 0.1‰, 0.2‰, 0.4‰, 0.8‰, and 1.6‰). The ASW improved the growth performance and increased the specific growth rate (SGR). Linear regression analysis based on the SGR estimated that the optimal ASW amount was 0.74‰. Dietary supplementation with 0.4–0.8‰ ASW reduced the triglyceride and total cholesterol levels in the serum and liver, and regulated lipid transport by increasing the high-density lipoprotein cholesterol concentration and lowering the low-density lipoprotein cholesterol concentration. Dietary supplementation with ASW increased the activities of superoxide dismutase and catalase in the liver, thereby improving the antioxidant capacity. Moreover, ASW modulated the transcription of genes in the peroxisome proliferator-activated receptor signaling pathway in the liver (upregulation of PPARα, APOA1b, and FABP10a and downregulation of PPARγ), thereby regulating fatty acid synthesis and metabolism and slowing fat deposition. These results showed that 0.4–0.8‰ ASW can slow fat deposition and protected the liver from cell damage and abnormal lipid metabolism.

The Protective Effects of Ganoderic Acids from Ganoderma lucidum Fruiting Body on Alcoholic Liver Injury and Intestinal Microflora Disturbance in Mice with Excessive Alcohol Intake

This study aimed to investigate the protective effects of ganoderic acids (GA) from Ganoderma lucidum against liver injury and intestinal microbial disorder in mice with excessive alcohol intake. Results showed GA supplement significantly inhibited the abnormal elevation of the liver index, serum lipid parameters, aspartate aminotransferase and alanine aminotransferase in mice exposed to alcohol intake, and also significantly protected the excessive lipid accumulation and pathological changes. Alcohol-induced oxidative stress in the liver was significantly ameliorated by GA intervention through reducing the levels of maleic dialdehyde and lactate dehydrogenase and increasing the levels of glutathione, catalase, superoxide dismutase and alcohol dehydrogenase. Intestinal microbiota profiling demonstrated GA intervention modulated the composition of intestinal microflora by increasing the levels of Lactobacillus, Faecalibaculum, Romboutsia, Bifidobacterium and decreasing the Helicobacter level. Furthermore, liver metabolomic profiling suggested GA intervention had a remarkable regulatory effect on liver metabolism with excessive alcohol consumption. Moreover, GA intervention regulated mRNA levels of alcohol metabolism, fatty lipid metabolism, oxidative stress, bile acid biosynthesis and metabolism-related genes in the liver. Conclusively, these findings demonstrate GA intervention can significantly relieve alcoholic liver injury and it is hopeful to become a new functional food ingredient for the prevention of alcoholic liver injury.

Key Performance Indicators of Common Carp (Cyprinus carpio L.) Wintering in a Pond and RAS under Different Feeding Schemes

Overwintering impacts common carp performance, yet the nature of changes is not known. The aim of the study was to compare the zootechnical and key performance indicators (KPI) of Cyprinus carpio wintering in a pond with no supplementary feeding (MCF), in a Recirculating Aquaculture System (RAS) fed typical (30% of protein and 8% of fat) carp diet (AFC), and in a RAS fed high protein (42%) and fat (12%) diet (ABF). The analysis showed that ABF fish had the highest final body weight and the Fulton’s condition factor, as well as the lowest food conversion rate compared with AFC and MCF fish. Histomorphological assessment revealed that MCF fish had thinner skin layers, a depleted population of mucous cells in skin, an excessive interlamellar mass in the gills, and no supranuclear vacuoles in the intestine compared to fish from RAS. At the molecular level, higher transcript levels of il-1β and il-6 transcripts were found in the gills of MCF than in fish from RAS. The transcript level of the intestinal muc5b was the highest in ABF fish. Relative expression of il-1β and il-6 in gills were presumably the highest due to lamellar fusions in MCF fish. Described KPIs may assist carp production to ensure sustainability and food security in the European Union.

Adsorptive removal of herbicides with similar structures from water over nitrogen-enriched carbon, derived from melamine@metal-azolate framework-6

Based on the recent concern on the pollution of water bodies with herbicides, adsorptive removal of typical herbicides with similar chemical structures, e. g. clofibric acid (CLFA), methylchlorophenoxypropionic acid or mecoprop (MCPP) and 2,4-dichlorophenoxyacetic acid (2,4-D) from water was studied using a porous nitrogen-enriched carbon. To prepare the nitrogen-enriched carbon, pyrolysis of a melamine (MLM) incorporated metal-azolate framework-6 (MLM(x)@MAF6; x = 0-50 M % of the ligand 2-ethylimidazole for MAF6), that was prepared for the first time via an in situ method, was carried out. The MLM(x)@MAF6-derived carbons (MDC6M(x)s) were characterized and used in the removal of CLFA, MCPP and 2,4-D from water. We found that the MDC6M(25), obtained from MLM(25)@MAF6 with 25% MLM (as the optimum precursor composition), showed the highest maximum adsorption capacity (Q₀) of 1031 mg/g for CLFA, compared with any reported adsorbents, so far. The physicochemical properties of CLFA, as well as adsorbents and adsorptions under wide pH conditions, were employed to propose a plausible adsorption mechanism including hydrogen bonding. Remarkably, the porous carbon with enriched nitrogen, derived from MAF6 loaded MLM via in situ method, was very competitive in herbicides adsorption because of the contribution of well-dispersed nitrogen sties on the adsorbent. Finally, MDC6M(25) was suggested as a potential adsorbent for the removal of herbcides, including CLFA, MCPP and 2,4-D, from water, which is highly attractive to mitigate the environmental issue, especially, water pollution by various herbicides.

Alterations in blood parameters, DNA damage, oxidative stress and antioxidant enzymes and immune-related genes expression in Nile tilapia (Oreochromis niloticus) exposed to glyphosate-based herbicide

In this study, effects of different concentrations (0, 5, 10, 20, 30, and 40 mg/L) of glyphosate-based herbicide (GBH) on Nile tilapia (Oreochromis niloticus) were investigated after a 14-day of exposure. After determination of LC50 value, effects of GBH on hematological and serum biochemical parameters in blood samples, DNA damage, lipid peroxidation and catalase activity in liver tissues, expression levels of antioxidant enzyme-related genes (SOD, CAT, GPx, and GST) and immune-related genes (TGF-β, TGF-α and IL1-β) were evaluated. The LC50 value has been found as 44.4 mg/L for GBH. GBH exposure at all concentrations caused alterations in blood parameters. GBH induced oxidative stress in liver and DNA damage in blood. Antioxidant enzyme-related genes were significantly up-regulated to suppress oxidative stress. On the other hand, the expression levels of immune-related genes decreased in fish exposure to particularly ≥20 mg/L GBH.

FABP regulates fatty acid metabolism and oxidative response via PPARα/RXR signaling in Litopenaeus vannamei following environmental exposure of clofibric acid

Clofibric acid (CFA), a drug and personal care product, has been identified as ubiquitous in the aquatic system and surface water, causing pollution to the environment. In this study, after environmental (4 µg/L) levels of CFA challenge, the LvFABP, LvACS gene expressions, total haemocyte count (THC), relative enzymes (SOD1 and GST) activities in Litopenaeus vannamei were observed to decrease. In the meantime LvFATP, LvRXR expression and the level of NEFA were upregulated in L. vannamei body. LvFABP expression in vivo was knocked down by dsRNA-mediated RNA interference (RNAi), which led to significantly decreased levels of PPARα (including LvFATP, LvRXR and LvACS). When exposed to environmental CFA after 4 days, LvFABP knocked down group had a sharp upregulation of LvFATP, LvRXR, LvACS expression, GST activity and NEFA amount, following decreased THC and SOD1 activity. These results suggested that environmental concentration CFA may have some toxicological effect on L. vannamei, following fatty acids metabolism and oxidative stress responses by LvFABP via the PPARα/RXR signaling pathway, including LvFATP, LvRXR and LvACS.

A comprehensive review of water quality monitoring and assessment in Nigeria

Nigeria is the most populated black nation in the world with about 199 million people. About 66.3 million Nigerians do not have access to safe drinking water. In this study, research findings on water quality monitoring and assessment in Nigeria over the past two decades were systematically reviewed. There are still grave enforcement issues in Nigeria as quality guidelines are still being contravened at no cost to the infringer due to the corrupt socio-political circumstances of the country. The quality of surface water, groundwater, rainwater and commercially available water was discussed in line with their pollution sources. The quality of surface water was generally poor. Groundwater pollution has come due to landfill leachate, oil and gas exploration and production, sewage and hydrogeological interactions of the groundwater with the base rock. The hydrogeological effect has led to the observation of lead and barium in groundwater in many locations across the country. The main issue with rainwater in Nigeria is the low pH but it was observed to be fairly clean. Commercially available water (bottled or sachet) is currently the best source of drinking water for the Nigerian populace. Bottled water quality is higher than for sachet water and the latter largely influenced by microbe contamination. Future perspectives in water quality monitoring and assessment are suggested in the evaluation of emerging contaminants and micro-pollutants and the utilisation of internet-enabled technologies.

Acute and chronic effects of environmental realistic concentrations of clofibric acid in Danio rerio: Behaviour, oxidative stress, biotransformation and lipid peroxidation endpoints

Due to their widespread use, pharmaceuticals can be metabolized, excreted and ultimately discarded in the environment, thereby affecting aquatic organisms. Lipid-regulating drugs are among the most prescribed medications around the world, controlling human cholesterol levels, in more than 20 million patients. Despite this growing use of lipid-regulating drugs, particularly those whose active metabolite is clofibric acid, the potential toxicological effects of these pharmaceuticals in the environment is not fully characterized. This work intended to characterize the toxicity of an acute (120 hours post-fertilization) and chronic (60 days post-fertilization) exposures to clofibric acid in concentrations of 10.35, 20.7, 41.4, 82.8, and 165.6 μg L^-1 in zebrafish (Danio rerio). The concentrations which were implemented in both exposures were based on predicted environmental concentrations for Portuguese surface waters. The acute effects were analysed focusing on behavioural endpoints (small and large distance travelled, swimming time and total distance travelled), biomarkers of oxidative stress (activity of the enzymes superoxide dismutase, Cu/Zn- and Mn SOD; catalase, CAT; glutathione peroxidase, Se- and total GPx), biotransformation (activity of glutathione S-transferases, GSTs) and lipid peroxidation (thiobarbituric acid reactive substances, TBARS). Chronically exposed individuals were also histologically analysed for sex determination and gonadal developmental stages. In terms of acute exposure, significant alterations were reported, in terms of behavioural alterations (hypoactivity), followed by an overall increase in all tested biomarkers. Chronically exposed organisms did not show alterations in terms of sex ratio and maturation stages, suggesting that clofibric acid did not act as an endocrine disruptor. Moreover, the metabolism of clofibric acid resulted in increased levels of both forms of SOD activity, especially for animals exposed to higher levels of this drug. An increase of CAT activity was observed in fish exposed to low levels, and a decrease in those exposed to higher amounts of clofibric acid. Both GPx forms had their activities increased. The enzyme of biotransformation GSTs were increased at low levels of clofibric acid but inhibited at higher amounts of this substance. Lipid peroxidation levels were also changed, with an induction of this parameter with increasing amounts of clofibric acid. Changes also occurred in behavioural endpoints and patterns for control organisms and for those exposed to clofibric acid were significantly distinct, for all types (light and darkness) of exposure, and for the two analysed endpoints (small and large distance). Results from this assay allow inferring that clofibric acid can have an ecologically relevant impact in living organisms exposed to this substance, with putative effects on the metabolism of individuals, affecting their behaviour and ultimately their survival.

Plasma biochemistry, gene expression and liver histomorphology in common carp (Cyprinus carpio) fed with different dietary fat sources

Demand for omega-3 long chain polyunsaturated fatty acids has become global challenge for aquaculture and different components have been used to increase nutritional value of fillets. The aim of this study was to evaluate influences of feeds on zootechnical parameters, biochemical plasma parameters, expression of lipid-dependent genes, hepatocyte histomorphologies, and fatty acid profiles in common carp fillets. We compared a control diet (CTRL), mimicking a commercial feed formulation for common carp, with three diets containing blends of vegetable oils and a DHA-rich alga (Schizochytrium sp.) included at 3.125% (CB1) or 1.563% (CB2), and 2.1% salmon oil (CB3). The study revealed no differences in final body weight of fish fed CB1-3 diets in comparison with significantly lower CTRL. Concentrations of all biochemical parameters in plasma increased gradually in fish fed CB1-3 diets when compared to CTRL diet, with exception of triacylglycerol levels. Expression of hepatic fas, elovl-5a and pparα genes increased significantly in fish fed CB1 and CB2. Additionally, eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) accumulation in muscle tissue was directly proportional to the amounts supplied in the diets. Our study revealed that carp fillet profiles can be manipulated for DHA and EPA-contents using enriched diets, depending on the source of fat.

Physiological status of silver carp (Hypophthalmichthys molitrix) in the Illinois River: An assessment of fish at the leading edge of the invasion front

Silver carp (Hypophthalmichthys molitrix) are invasive to North America, and their range has expanded within the Mississippi River Basin, seemingly unchecked, since their introduction in the late 1970s, with the exception of the upper reaches of the Illinois River. With the imminent threat of their movement into the Great Lakes, the goal of the present study was to assess whether differences in the physiological status between silver carp at the leading edge of their invasion front and core population sites could explain their lack of expansion upstream toward Lake Michigan over the past decade. A transcriptomic approach using RNA sequencing and analysis of plasma variables were used to quantify differences among fish at the leading edge and two downstream core population sites. Leading-edge fish exhibited upregulation of genes associated with xenobiotic defense (e.g., ATP-binding cassette C1 [abcc1], abcc2, abcc6), decreased cell integrity (i.e., macroautophagy and apoptosis; autophagy-related protein 9A [atg9a], caspase 3b [casp3b]), and cholesterol metabolism (e.g., abca1, apolipoprotein A1 [apoa1], sterol O-acyltransferase [soat1]) and downregulation of genes associated with DNA repair (e.g., tumor suppressor p53-binding protein 1 [tp53bp1]) compared to core population sites. Transcriptomic profiles of leading-edge fish were consistent with fish inhabiting a polluted environment and suggest that poorer water quality conditions upstream of the leading edge may represent a non-permanent barrier to silver carp range expansion. The present study provides potential molecular targets for monitoring the physiological status of silver carp over time and in response to future improvements in water quality upstream of their leading edge.

Effects of gemfibrozil on sex hormones and reproduction related performances of Oryzias latipes following long-term (155 d) and short-term (21 d) exposure

Gemfibrozil, a lipid-regulating pharmaceutical, has been widely used for treating dyslipidemia in humans and detected frequently in freshwater environments. Since plasma cholesterol is a precursor of steroid hormones, the use of gemfibrozil may influence the sex hormone balances. However, its endocrine toxicity following long-term exposure is not well understood. The purpose of the present study is to investigate the effects of gemfibrozil on sex hormones and reproductive outcomes in a freshwater fish, following a long-term (155 d) exposure. For this purpose, Japanese medaka embryos (F0) were exposed to a series of gemfibrozil concentrations, i.e., 0, 0.04, 0.4, 3.7, and 40 mg/L for 155 d, and reproductive parameters, sex hormones, and associated gene expressions were assessed. For comparison, a short-term exposure (21 d) was performed separately with adult medaka and measured for sex hormones and related gene expressions. Following the 155 d long-term exposure, the fecundity showed a decreasing pattern. In addition, at 3.7 mg/L gemfibrozil, testosterone (T) level in the female fish was significantly decreased, and the hatchability of F1 fish was significantly decreased. The estrogen receptor (er) or vitellogenin (vtg) genes in gonads and liver were up-regulated. However, plasma cholesterol levels did not show significant changes in both sexes. The observations from the short-term (21 d) exposure were different from those of the long-term exposure. Following the short-term exposure, decreased 17β-estradiol (E2), and 11-ketotestosterone (11-KT) levels along with decrease plasma cholesterol were observed in the male fish. The hormone disruption following the short-term exposure appears to be associated with the hypocholesterolemic activity of gemfibrozil. Our results show that the mechanisms of gemfibrozil toxicity may depend on the exposure duration. Consequences of long-term exposure to other fibrates in the water environment warrant further investigations.

Transcriptomics analysis reveals candidate genes and pathways for susceptibility or resistance to Singapore grouper iridovirus in orange-spotted grouper (Epinephelus coioides)

In this study, the transcriptional response of grouper to Singapore grouper iridovirus (SGIV) stimulation was characterized using RNA sequencing. Transcriptome sequencing of three test groups in the grouper was performed using the Illumina MiSeq platform. The three test groups were a control group, which was injected with PBS buffer; a high-susceptible (HS) group, which died shortly after the SGIV injection; and a high-resistance (HR) group, which survived the SGIV injection. In total, 38,253 unigenes were generated. When the HS group was compared with the control group, 885 unigenes were upregulated and 487 unigenes were downregulated. When the HR and control groups were compared, 1114 unigenes were upregulated and 420 were downregulated, and when the HR and HS groups were compared, 1010 unigenes were upregulated and 375 were downregulated. In the KEGG analysis, two immune-related pathways, the p53 and peroxisome proliferator-activated receptor pathways, were detected with highly significant enrichment. In addition, 7465 microsatellites and 22,1569 candidate single nucleotide polymorphisms were identified from our transcriptome data. The results suggested several pathways that are associated with traits of disease susceptibility or disease resistance, and provided extensive information about novel gene sequences, gene expression profiles, and genetic markers. This may contribute to vaccine research and a breeding program against SGIV infection in grouper.

Ethanol extract of Ganoderma lucidum ameliorates lipid metabolic disorders and modulates the gut microbiota composition in high-fat diet fed rats

The objective of this study was to investigate the effects of ethanol extract of Ganoderma lucidum (GL95) on hyperlipidaemia and gut microbiota, and its regulation mechanism in Wistar rats fed on a high-fat diet (HFD). UPLC-QTOF MS indicated that GL95 was enriched with triterpenoids, especially ganoderic acids. The results of the animal experiment showed that oral administration of GL95 markedly alleviated the dyslipidemia through decreasing the levels of serum total triglyceride (TG), total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C), and inhibiting hepatic lipid accumulation and steatosis. Furthermore, GL95 supplementation altered the composition of gut microbiota, in particular modulating the relative abundance of functionally relevant enterotypes compared with the HFD group. The Spearman's correlation analysis revealed that Alistipes, Defluviitalea, Peptococcaceae and Alloprevotella were negatively correlated with serum and hepatic lipid profiles. Meanwhile, the GL95 treatment regulated the mRNA expression levels of the genes involved in lipid and cholesterol metabolism. The findings above illustrate that Ganoderma triterpenoids have the potential to ameliorate lipid metabolic disorders, in part through modulating specific gut microbiota and regulating the genes involved in lipid and cholesterol metabolism, suggesting Ganoderma triterpenoids as a potential novel functional food for the treatment or prevention of hyperlipidaemia.

Growth, energy metabolism and transcriptomic responses in Chinese mitten crab (Eriocheir sinensis) to benzo[α]pyrene (BaP) toxicity

Benzo(a)pyrene (BaP) is a highly toxic polycyclic aromatic hydrocarbon and has strong affinity to suspended materials and sediments in the aquatic environment. Most crustaceans are benthic species and are easily affected by the pollution in the sediments, but there is little information on the response mechanism of crustaceans to BaP exposure. This study compared the growth and hepatopancreas transcriptomic responses of the Chinse mitten crab (Eriocheir sinensis) exposed to 0, 0.15 (BaP1) and 0.45 μg /L (BaP2) for 28 days. Crab survival and weight gain were reduced in the water born BaP in a dose-dependent way. The contents of hepatopancreas glycogen, triglyceride, total amino acids and lactic acid were all decreased after BaP exposure, indicating possible more energy consumption during detoxification. In the transcriptome analysis, a total of 106.65 million clean reads were obtained and assembled into 81,714 unigenes with an average length of 594 bp and N50 of 808 bp. Under 0.15 or 0.45 μg /L BaP exposure, 922 and 1129 unigenes in crabs were significantly expressed, annotated to 676 and 802 Gene Ontology (GO) terms respectively. The "cellular process" was the leading category for both concentrations. Thirteen significantly changed pathways were identified in both Control vs BaP1 and Control vs BaP2 groups. These pathways were divided into four different parts according to their reported functions, including metabolism, environmental information processing, organismal systems and cellular processes. Nice out of thirteen pathways in BaP1 were related to metabolism, containing amino acid metabolism, phenylpropanoid biosynthesis, monobactam biosynthesis and styrene degradation. Almost all the pathways related with the biosynthesis processes were down-regulated, while the degradation pathways were up-regulated. Seven out of thirteen pathways were classified into metabolism category in BaP2. These pathways were mostly associated with stress resistance rather than supplying energy. This study indicates that both concentrations of BaP disturbed nutrient metabolism, immune response and defense system in the crabs, while exposure to a higher concentration had a greater impact on immunity system than on metabolism. This study provides a better understanding of the underlying molecular and regulatory mechanisms in crustaceans coping with BaP toxicity.

Effect of pore structure on the removal of clofibric acid by magnetic anion exchange resin

The effect of pore structure of resin on clofibric acid (CA) adsorption behavior was investigated by using magnetic anion exchange resins (ND-1, ND-2, ND-3) with increasing pore diameter by 11.68, 15.37, 24.94 nm. Resin with larger pores showed faster adsorption rates and a higher adsorption capacity because the more opened tunnels provided by larger pores benefit the CA diffusion into the resin matrix. The ion exchange by the electrostatic interactions between Cl-type resin and CA resulted in chloride releasing to the solution, and the ratio of released chloride to CA adsorption amount decreased from 0.90 to 0.65 for ND-1, ND-2 and ND-3, indicating that non-electrostatic interactions obtain a larger proportional part of the adsorption into the pores. Co-existing inorganic anions and organic acids reduced the CA adsorption amounts by the competition effect of electrostatic interaction, whereas resins with more opened pore structures weakened the negative influence on CA adsorption because of the existence of non-electrostatic interactions. 85.2% and 65.1% adsorption amounts decrease are calculated for resin ND-1 and ND-3 by the negative influence of 1 mmol L^-1 NaCl. This weaken effect of organic acid is generally depends on its hydrophobicity (Log Kow) for carboxylic acid and its ionization degree (pKb) for sulfonic acid. The resins could be reused with the slightly decreases by 1.9%, 3.2% and 5.4% after 7 cycles of regeneration, respectively for ND-1, ND-2 and ND-3, suggesting the ion exchange resin with larger pores are against its reuse by the brine solution regeneration.

Effects of stocking density on lipid deposition and expression of lipid-related genes in Amur sturgeon (Acipenser schrenckii)

To investigate the correlation between lipid deposition variation and stocking density in Amur sturgeon (Acipenser schrenckii) and the possible physiological mechanism, fish were conducted in different stocking densities (LSD 5.5 kg/m³, MSD 8.0 kg/m³, and HSD 11.0 kg/m³) for 70 days and then the growth index, lipid content, lipase activities, and the mRNA expressions of lipid-related genes were examined. Results showed that fish subjected to higher stocking density presented lower final body weights (FBW), specific growth ratio (SGR), and gonad adipose tissue index (GAI) (P < 0.05). Lower lipid content was observed in the liver, gonad adipose tissue and muscle in sturgeons held in HSD group (P < 0.05). The serum concentrations of triglyceride (TG), total cholesterol (TC), and high-density lipoprotein cholesterol (HDL-C) decreased significantly with increasing stocking density, while no significant change was observed for low-density lipoprotein cholesterol (LDL-C). Furthermore, the cDNAs encoding lipoprotein lipase (LPL) and hepatic lipase (HL) were isolated in Amur sturgeon, respectively. The full-length LPL cDNA was composed of 1757 bp with an open reading frame of 501 amino acids, while the complete nucleotide sequences of HL covered 1747 bp encoding 499 amino acids. In the liver, the activities and mRNA levels of LPL were markedly lower in HSD group, which were consistent with the variation tendency of HL. Fish reared in HSD group also presented lower levels of activities and mRNA expression of LPL in the muscle and gonad. Moreover, the expressions of peroxisome proliferator-activated receptor α (PPARα) in both the liver and skeletal muscle were significantly upregulated in HSD group. Overall, the results indicated that high stocking density negatively affects growth performance and lipid deposition of Amur sturgeon to a certain extent. The downregulation of LPL and HL and the upregulation of PPARα may be responsible for the lower lipid distribution of Amur sturgeon in higher stocking density.

Obesogens in the aquatic environment: an evolutionary and toxicological perspective

The rise of obesity in humans is a major health concern of our times, affecting an increasing proportion of the population worldwide. It is now evident that this phenomenon is not only associated with the lack of exercise and a balanced diet, but also due to environmental factors, such as exposure to environmental chemicals that interfere with lipid homeostasis. These chemicals, also known as obesogens, are present in a wide range of products of our daily life, such as cosmetics, paints, plastics, food cans and pesticide-treated food, among others. A growing body of evidences indicates that their action is not limited to mammals. Obesogens also end up in the aquatic environment, potentially affecting its ecosystems. In fact, reports show that some environmental chemicals are able to alter lipid homeostasis, impacting weight, lipid profile, signaling pathways and/or protein activity, of several taxa of aquatic animals. Such perturbations may give rise to physiological disorders and disease. Although largely unexplored from a comparative perspective, the key molecular components implicated in lipid homeostasis have likely appeared early in animal evolution. Therefore, it is not surprising that the obesogen effects are found in other animal groups beyond mammals. Collectively, data indicates that suspected obesogens impact lipid metabolism across phyla that have diverged over 600 million years ago. Thus, a consistent link between environmental chemical exposure and the obesity epidemic has emerged. This review aims to summarize the available information on the effects of putative obesogens in aquatic organisms, considering the similarities and differences of lipid homeostasis pathways among metazoans, thus contributing to a better understanding of the etiology of obesity in human populations. Finally, we identify the knowledge gaps in this field and we set future research priorities.

Effects of diclofenac on the expression of Nrf2 and its downstream target genes in mosquito fish (Gambusia affinis)

Diclofenac (DCF) is one of widely used non-steroidal anti-inflammatory drugs. Recently, this drug has been universally detected in aquatic environment. However, its potential adverse effects and oxidative stress toxic mechanisms on fish remain unclear. In the present study, we first cloned the crucial partial sequences of some key oxidative stress related genes, which include NF-E2-related factor 2 (Nrf2), NAD(P)H: quinoneoxidoreductase (NQO1), glutamate-cysteine ligase catalytic subunit (GCLC), Cu-Zn superoxide dismutase (SOD2), catalase (CAT), alpha-glutathione S-transferase (GSTA), and UDP-glucuronosyltransferases (UGT) in mosquito fish (Gambusia affinis). We also deduced amino acids of Nrf2 and then constructed the phylogenetic trees of Nrf2, NQO1 and GCLC, respectively. Results showed that a high identity percentage was founded between G. affinis and other bony fish species, such as Xiphophorus maculates and Poecilia reticulate. The transcriptional expression of these genes and partly related enzymes activities were then investigated under the included environmental relevant concentration DCF exposure (0μmolL^-1, 1.572×10^-3μmolL^-1, 1.572×10^-2μmolL^-1, 0.1572μmolL^-1 and 1.572μmolL^-1) for 24h and 168h. The expression of Nrf2 was inhibited at 24h but induced at 168h, exhibiting a significant time and/or dose-effect relationship under DCF exposure. Similar observation was found in its downstream target genes. However, Nrf2-mediated antioxidant enzymes activities displayed differently under the same concentration of DCF exposure for the same time. Under DCF exposure for 168h, the genes exhibited dramatic induction trend, but there were no significant changes in enzyme activities and MDA content. Overall, mRNA responses were more sensitive than enzyme changes in mosquito fish under DCF exposure.

Neurotoxic effects, molecular responses and oxidative stress biomarkers in Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) exposed to verapamil

Pharmaceutical drugs and their metabolites are detected in aquatic ecosystems and have been reported to cause ecotoxicological consequences to resident aquatic organisms. The study investigated the effects of acute and long-term exposure to verapamil on activities of acetylcholinesterase and antioxidant enzymes as well as mRNA expression of stress-related genes in brain and muscle tissues of Nile tilapia, Oreochromis niloticus. The 96h LC₅₀ of verapamil to O. niloticus was 2.29mgL^-1. Exposure to sub-lethal concentrations of verapamil (0.14, 0.29 and 0.57mgL^-1) for period of 15, 30, 45 and 60days, led to inhibition of acetylcholinesterase activities in the brain and muscle of the fish. The activities of the oxidative enzymes such as the catalase, superoxide dismutase and glutathione peroxidase were also inhibited in both the tissues while there was an increase in the activities of glutathione-S-transferase and reduced glutathione in the muscle after 15 days at 0.29mgL^-1. Lipid peroxidation and carbonyl protein showed elevated level, indicating a positive correlation with both time and concentration. The activities of energy-related biomarker (Na⁺-K⁺-ATPase) in both the tissues were significantly inhibited (p<0.05) compared with the control. Transcription of catalase (cat), superoxide dismutase (sod) and heat shock proteins 70 (hsp70) were up-regulated in both the tissues after the study period. Prolonged exposure to sub-lethal verapamil can result in oxidative stress, up-regulation of stress-related genes and neurotoxicity in O. niloticus.

Cross-interference of two model peroxisome proliferators in peroxisomal and estrogenic pathways in brown trout hepatocytes

Peroxisome proliferators cause species-specific effects, which seem to be primarily transduced by peroxisome proliferator-activated receptor alpha (PPARα). Interestingly, PPARα has a close interrelationship with estrogenic signaling, and this latter has already been promptly activated in brown trout primary hepatocytes. Thus, and further exploring this model, we assess here the reactivity of two PPARα agonists in direct peroxisomal routes and, in parallel the cross-interferences in estrogen receptor (ER) mediated paths. To achieve these goals, three independent in vitro studies were performed using single exposures to clofibrate - CLF (50, 500 and 1000μM), Wy-14,643 - Wy (50 and 150μM), GW6471 - GW (1 and 10μM), and mixtures, including PPARα agonist or antagonist plus an ER agonist or antagonist. Endpoints included gene expression analysis of peroxisome/lipidic related genes (encoding apolipoprotein AI - ApoAI, fatty acid binding protein 1 - Fabp1, catalase - Cat, 17 beta-hydroxysteroid dehydrogenase 4 - 17β-HSD4, peroxin 11 alpha - Pex11α, PPARαBb, PPARαBa and urate oxidase - Uox) and those encoding estrogenic targets (ERα, ERβ-1 and vitellogenin A - VtgA). A quantitative morphological approach by using a pre-validated catalase immunofluorescence technique allowed checking possible changes in peroxisomes. Our results show a low responsiveness of trout hepatocytes to model PPARα agonists in direct target receptor pathways. Additionally, we unveiled interferences in estrogenic signaling caused by Wy, leading to an up-regulation VtgA and ERα at 150μM; these effects seem counteracted with a co-exposure to an ER antagonist. The present data stress the potential of this in vitro model for further exploring the physiological/toxicological implications related with this nuclear receptor cross-regulation.

Method for quantifying NSAIDs and clofibric acid in aqueous samples, lumpfish (Cyclopterus lumpus) roe, and zebrafish (Danio rerio) eleutheroembryos and evaluation of their bioconcentration in zebrafish eleutheroembryos

Pharmaceuticals such as nonsteroidal anti-inflammatory drugs (NSAIDs) and lipid regulators are being repeatedly detected at low concentrations (pg · mL^-1-ng · mL^-1) in the environment. A large fraction of these compounds are ionizable. Ionized compounds show different physico-chemical properties and environmental behavior in comparison to their neutral analogs; as a consequence, the quantification methods currently available, based on the neutral molecules, might not be suitable to detect the corresponding ionized compounds. To overcome this problem, we developed a specific analytical method to quantify NSAIDs and lipid regulators (i.e., ibuprofen, diclofenac, naproxen, and clofibric acid) and their ionized compounds. This method is based on three steps: (1) the extraction of the organic compounds with an organic solvent assisted with an ultrasonic probe, (2) the cleaning of the extracts with a dispersive SPE with C₁₈, and (3) the determination of the chemical compounds by GC-MS (prior derivatization of the analytes). We demonstrated that the proposed method can successfully quantify the pharmaceuticals and their ionized compounds in aqueous samples, lumpfish eggs, and zebrafish eleutheroembryos. Additionally, it allows the extraction and the cleanup of extracts from small samples (0.010 g of wet weight in pools of 20 larvae) and complex matrixes (due to high lipid content) and can be used as a basis for bioaccumulation assays performed with zebrafish eleutheroembryos in alternative to OECD test 305.

Development of a common carp (Cyprinus carpio) pregnane X receptor (cPXR) transactivation reporter assay and its activation by azole fungicides and pharmaceutical chemicals

In mammals, the pregnane X receptor (PXR) is a transcription factor with a key role in regulating expression of several genes involved in drug biotransformation. PXR is present in fish and some genes known to be under its control can be up-regulated by mammalian PXR ligands. Despite this, direct involvement of PXR in drug biotransformation in fish has yet to be established. Here, the full length PXR sequence was cloned from carp (Cyprinus carpio) and used in a luciferase reporter assay to elucidate its role in xenobiotic metabolism in fish. A reporter assay for human PXR (hPXR) was also established to compare transactivation between human and carp (cPXR) isoforms. Rifampicin activated hPXR as expected, but not cPXR. Conversely, clotrimazole (CTZ) activated both isoforms and was more potent on cPXR, with an EC50 within the range of concentrations of CTZ measured in the aquatic environment. Responses to other azoles tested were similar between both isoforms. A range of pharmaceuticals tested either failed to activate, or were very weakly active, on the cPXR or hPXR. Overall, these results indicate that the cPXR may differ from the hPXR in its responses and/or sensitivity to induction by different environmental chemicals, with implications for risk assessment because of species differences.

Assessing the phototransformation of diclofenac, clofibric acid and naproxen in surface waters: Model predictions and comparison with field data

Phototransformation is important for the fate in surface waters of the pharmaceuticals diclofenac (DIC) and naproxen (NAP) and for clofibric acid (CLO), a metabolite of the drug clofibrate. The goal of this paper is to provide an overview of the prevailing photochemical processes, which these compounds undergo in the different conditions found in freshwater environments. The modelled photochemical half-life times of NAP and DIC range from a few days to some months, depending on water conditions (chemistry and depth) and on the season. The model indicates that direct photolysis is the dominant degradation pathway of DIC and NAP in sunlit surface waters, and potentially toxic cyclic amides were detected as intermediates of DIC direct phototransformation. With modelled half-life times in the month-year range, CLO is predicted to be more photostable than DIC or NAP and to be degraded mainly by reaction with the ^•OH radical and with the triplet states of chromophoric dissolved organic matter (³CDOM*). The CLO intermediates arising from these processes and detected in this study (hydroquinone and 4-chlorophenol) are, respectively, a chronic toxicant to aquatic organisms and a possible carcinogen for humans. Hydroquinone is formed with only ∼5% yield upon CLO triplet-sensitised transformation, but it is highly toxic for algae and crustaceans. In contrast, the formation yield of 4-chlorophenol reaches ∼50% upon triplet sensitisation and ∼10% by ^·OH reaction. The comparison of model predictions with field data from a previous study yielded a very good agreement in the case of DIC and, when using 4-carboxybenzophenone as proxy for triplet sensitisation by CDOM, a good agreement was found for CLO as well. In the case of NAP, the comparison with field data suggests that its direct photolysis quantum yield approaches or even falls below the lower range of literature values.

Evaluation of gemfibrozil effects on a marine fish (Sparus aurata) combining gene expression with conventional endocrine and biochemical endpoints

The information on the potential hazardous effects of gemfibrozil (GEM) on marine fish is extremely scarce. In the current study, molecular, endocrine and biochemical parameters were assessed in Sparus aurata after 96h waterborne exposure to a GEM concentration range. Hepatic mRNA levels of target genes known to be regulated via peroxisome proliferator-activated receptor α (pparα) in mammals, such as apolipoprotein AI (apoa1) and lipoprotein (lpl) were significantly increased, without a concomitant activation of the ppar pathways. GEM (15μgL(-1)) induced an upregulation in mRNA levels of interleukin 1β (il1β), tumour necrosis factor-α (tnfα) and caspase 3 (casp3), suggesting an activation of proinflammatory processes in S. aurata liver. However, mRNA levels of genes related with the antioxidant defence system and cell-tissue repair were unaltered under the tested experimental conditions. Higher levels of GEM induced a cortisol rise, an indication that it is recognized as a stressor by S. aurata. Cortisol levels and the mRNA levels of il1β, tnfα and casp3 may be suggested as potential biomarkers of GEM effects in marine fish.

Fatty acid metabolism in fish species as a biomarker for environmental monitoring

Pollution by Organic Contaminants (OC) in aquatic environments is a relevant issue at the global scale. Lipids comprised of Fatty Acids (FA) play many important roles in the physiology and life history of fishes. Toxic effects of OC are partly dependent on its bioaccumulation in the lipids of aquatic organisms due its physicochemical properties. Therefore, there is an increasing interest to investigate the gene expression as well as the presence and activity of proteins involved in FA metabolism. The attention on Peroxisome Proliferation Activate Receptors (PPARs) also prevails in fish species exposed to OC and in the transport, biosynthesis and β-oxidation of FA. Several studies have been conducted under controlled conditions to evaluate these biological aspects of fish species exposed to OC, as fibrates, endocrine disrupting compounds, perfluoroalkyl acids, flame retardants, metals and mixtures of organic compounds associated with a polluted area. However, only fibrates, which are agonists of PPARs, induce biological responses suitable to be considered as biomarkers of exposure to these pollutants. According to the documented findings on this topic, it is unlikely that these physiological aspects are suitable to be employed as biomarkers with some noticeable exceptions, which depend on experimental design. This emphasises the need to investigate the responses in fish treated with mixtures of OC and in wild fish species from polluted areas to validate or refute the suitability of these biomarkers for environmental or fish health monitoring.

Oxidative stress and immune disturbance after long-term exposure to bisphenol A in juvenile common carp (Cyprinus carpio)

Bisphenol A (BPA) is a well-known endocrine disrupting chemical (EDC), ubiquitous in the aquatic environment, which poses an ecotoxicological risk to the health of aquatic organisms. However, the immunotoxic effects of its long-term exposure on fish have received limited attention. We examined a number of typical immune-related parameters and oxidative stress indices in the liver and blood serum of the red common carp (Cyprinus carpio), following a 30-day exposure to five different concentrations of BPA (0.1, 1, 10, 100, and 1000μg/L). A significant increase in the hepato somatic index was observed in fish upon exposure to 1000µg/L BPA, which correlated strongly with the accumulated BPA concentrations in fish bile. Induced oxidative stress was also apparent in the exposed fish liver, based on the enhanced levels of lipid peroxidation and inhibited activities of catalase, superoxide dismutase, and glutathione peroxidase. Serum lysozyme and C-reaction protein levels increased at low concentrations of exposure; however, they were significantly suppressed upon exposure to high concentrations. A significant increase was observed in the levels of immunoglobulin M, complement component 3, and alkaline phosphatase, in both fish liver and serum at low doses of 0.1 and 1μg/L. This suggests that long-term exposure to environmentally relevant concentrations of BPA (even as low as 0.1μg/L) could significantly disturb the immune response of fish. Moreover, RXRα expression in the liver was significantly altered upon BPA exposure and the trend underlying this change correlated closely with those of the most immune-related parameters, implying the involvement of the PPARγ/RXRα signaling pathway in regulating the immune response of fish upon long-term BPA exposure. In short, our results demonstrate the susceptibility of fish immune system to long-term BPA exposure. Therefore, the immunotoxicity of EDCs in aquatic organisms should not have been underestimated.

ABC transporters and xenobiotic defense systems in early life stages of rainbow trout (Oncorhynchus mykiss)

Embryos of oviparous fish, in contrast to (ovo) viviparous species, develop in the aquatic environment, and therefore need solute transport systems at their body surfaces for maintaining internal homeostasis and defending against potentially harmful substances. We hypothesized that solute transporters undergo changes in tissue distribution from the embryo to the larval stage. We therefore studied the mRNA profiles of eight ABC transporters (abcb1a, abcb1b, abcc1, abcc2, abcc3, abcc4, abcc5, abcg2) and three solute carriers (oatp1d, putative oatp2 putative, mate1) in different body regions (head, yolk sac epithelium, abdominal viscera, skin/muscles) of developing rainbow trout. Additionally, we investigated mRNA levels of phase I (cyp1a, cyp3a) and phase II (gstp, putative ugt1, putative ugt2) biotransformation enzymes. The study covered the developmental period from the eleuthero-embryo stage to the first-feeding larval stage (1-20days post-hatch, dph). At 1dph, transcripts of abcc2, abcc4, abcg2, cyp3a, gstp, putative mate1, and putative oatp2 occurred primarily in the yolk sac epithelium, whereas at later stages expression of these genes was predominantly observed in the abdominal viscera. The functional activity of ABC transporters in fish early life stages was assessed by rhodamine B accumulation assays. Finally, we investigated the potential impact of xenobiotics (clotrimazole, clofibric acid) on the ABC and biotransformation systems of trout early life stages. While clofibric acid had no effect, clotrimazole lead to an increased rhodamine B accumulation. The results provide evidence that the transition from the eleuthero-embryo to the larval stage is accompanied by a major alteration in tissue expression of ABC transporters.

Tri-m-cresyl phosphate and PPAR/LXR interactions in seabream hepatocytes: revealed by computational modeling (docking) and transcriptional regulation of signaling pathways

The interactions between tri-m-cresyl phosphate (TMCP; an organophosphate flame retardant) and peroxisome proliferator activated receptors (PPARs) or liver X receptor α (LXRα) were investigated in seabream hepatocytes. The study was designed to characterize the binding of TMCP to PPARα, PPARγ and LXRα by computational modeling (docking) and transcriptional regulation of signaling pathways. TMCP mainly established a non-polar interaction with each receptor. These findings reflect the hydrophobic nature of this binding site, with fish LXRα showing the highest binding efficiency. Further, we have investigated the ability of TMCP to activate PPAR and LXR controlled transcriptional processes involved in lipid/cholesterol metabolism. TMCP induced the expression of all the target genes measured. All target genes were up-regulated at all exposure doses, except for fatty acid binding protein 7 (FABP7) and carnitine palmitoyltransferase 1B. Collectively, our data indicate that TMCP can affect fatty acid synthesis/uptake and cholesterol metabolism through LXRα and PPARs, together with interactions between these transcription factors in seabream liver.