Effects of alkylphenols on glycerophospholipids and cholesterol in liver and brain from female Atlantic cod (Gadus morhua)

Pharmacodynamic Evaluation and Mechanism of Ginseng Polysaccharide against Nephrotoxicity Induced by Hexavalent Chromium

Hexavalent chromium is a common pollutant in the environment. Long-term exposure to hexavalent chromium can cause damage to multiple organs. The kidney is one of the main organs that metabolizes heavy metal toxicity, and the accumulation of Cr (VI) in the body can lead to serious damage to kidney function. Studies have shown that ginseng polysaccharides have the function of preventing cisplatin-induced endoplasmic reticulum stress, inflammatory response, and apoptosis in renal cells, but their efficacy and mechanisms against hexavalent chromium-induced nephrotoxicity need to be explored. The aim of this study was to explore the efficacy and mechanism of ginseng polysaccharide against hexavalent chromium-induced nephrotoxicity. The results of pharmacodynamic experiments showed that ginseng polysaccharide could significantly reduce the kidney index, urea nitrogen (BUN), and serum creatinine (Cre) values of K2Cr2O7-treated mice. The results of mechanistic experiments showed that ginseng polysaccharides could alleviate oxidative stress, apoptosis, and biofilm damage in renal tissues caused by Cr (VI). Lipidomic correlation analysis showed that ginseng polysaccharides could protect the organism by regulating the expression of differential lipids. This study opens new avenues for the development of alternative strategies for the prevention of kidney injury caused by hexavalent chromium.

Hepatoprotective effects of peach gum polysaccharides against alcoholic liver injury: moderation of oxidative stress and promotion of lipid metabolism

Natural polysaccharides extracted from plants have received increasing attention due to their rich bioactivity. In our study, peach gum polysaccharides (PGPs) were extracted by water extraction-alcohol precipitation method. PGPs are typical pyranose polysaccharides with a mean molecular weight of 3.68 × 106 g/mol. The antioxidant activity and hepatoprotective capacity of PGPs were studied. In vitro, assays showed that PGPs scavenged DPPH, OH, and O2- in a dose-dependent manner. PGPs exhibited antioxidative properties against alcohol-induced HL7702 cells, as evidenced by the normalization of MDA, SOD, ROS, and GSH levels. To further elucidate the hepatoprotective mechanism of PGPs, we carried out in vivo experiments in male mice. PGPs exerted hepatoprotective effects in alcohol liver disease (ALD) mice by exerting antioxidant effects, decreasing the inflammatory response and modulating lipid metabolism. In addition, metabolomic analysis indicated that PGPs mainly regulate D-glutamine and D-glutamate metabolism, alanine, aspartate and glutamate metabolism, and arginine biosynthesis to promote hepatic metabolism and maintain body functions. Overall, this study revealed that the hepatoprotective mechanism of PGPs against ALD might be associated with the regulation of oxidative stress and lipid metabolism.

Effects of chronic crude oil exposure on the fitness of polar cod (Boreogadus saida) through changes in growth, energy reserves and survival

Climate models predict extended periods with sea-ice free Arctic waters during the next decade, which will allow more shipping activity and easier access to petroleum resources. Increased industrial activities raise concerns about the biological effects of accidental petroleum release on key species of the Arctic marine ecosystem, such as the polar cod (Boreogadus saida). This study examines effects on physiological traits related to the fitness of adult polar cod, such as growth, survival, and lipid parameters. Fish were exposed to environmentally-relevant crude oil doses through their diet over an 8-month period, concurrent with reproductive development. In liver tissue, lipid class composition differed between treatments while in gonad tissue, lipid class composition varied between sexes, but not treatments. Crude oil did not affect growth and survival, which indicated that polar cod were relatively robust to dietary crude oil exposure at doses tested (0.11-1.14 μg crude oil/g fish/day) in this study.

Cardiac dysfunction affects eye development and vision by reducing supply of lipids in fish

Developing organisms are especially vulnerable to environmental stressors. Crude oil exposure in early life stages of fish result in multiple functional and developmental defects, including cardiac dysfunction and abnormal and smaller eyes. Phenanthrene (Phe) has a reversible impact on cardiac function, and under exposure Phe reduces cardiac contractility. Exposure to a known L-type channel blocker, nicardipine hydrochloride (Nic) also disrupts cardiac function and creates eye deformities. We aimed to investigate whether cardiac dysfunction was the major underlying mechanism of crude oil-, Phe- and Nic-induced eye malformations. We exposed Atlantic haddock (Melanogrammus aeglefinus) early embryos to Nic and crude oil (Oil) and late embryos/early larvae to Phe exposure. All three exposures resulted in cardiac abnormalities and lead to severe, eye, jaw and spinal deformities at early larval stages. At 3 days post hatching, larvae from the exposures and corresponding controls were dissected. Eyes, trunk, head and yolk sac were subjected to lipid profiling, and eyes were also subjected to transcriptomic profiling. Among most enriched pathways in the eye transcriptomes were fatty acid metabolism, calcium signaling and phototransduction. Changes in lipid profiles and the transcriptome suggested that the dysfunctional and abnormal eyes in our exposures were due to both disruption of signaling pathways and insufficient supply of essential fatty acids and other nutrients form the yolk.

4-Hexylphenol influences adipogenic differentiation and hepatic lipid accumulation in vitro

Finding the potential environmental obesogens is crucial to explain the prevalence of obesity and the related pathologies. Increasing evidence has showed that many chemicals with endocrine disrupting effects can disturb lipid metabolism. Whether 4-hexylphenol (4-HP), a widely-used surfactant and a potential endocrine disrupting chemical (EDC), is associated to influence adipogenesis and hepatic lipid accumulation remained to be elucidated. In this study, both the 3T3-L1 differentiation model and oleic acid (OA)-treated HepG2 cells were used to investigate the effects of 4-HP on lipid metabolism, and the underlying estrogen receptor (ER)-involved mechanism was explored using MVLN assay, molecular docking simulation and the antagonist test. The results based on lipid droplet staining and triglyceride accumulation assay showed that 4-HP treatment promoted the adipogenic differentiation of 3T3-L1 cells and increased hepatic cellular OA accumulation in exposure concentration-dependent manners. The study on the elaborated transcription networks indicated that 4-HP activated peroxisome proliferator-activated receptor γ (PPARγ) as well as the subsequent adipogenic gene program in 3T3-L1 cells. This chemical also induced the increase of OA uptake and decreases of de novo lipogenesis and fatty acid oxidation in HepG2 cells. The agonistic activity of 4-HP in triggering ER-mediated pathway was shown to correlate with its perturbation in lipid metabolism, as evidenced by the enhanced development of mature lipid-laden adipocytes and suppression of excessive hepatic lipid accumulation upon its co-treatment with ER antagonist. Altogether, these findings provide new insights into the potential health impacts of 4-HP exposure as it may relate to obesity and nonalcoholic fatty liver disease.

Environmental effects of offshore produced water discharges: A review focused on the Norwegian continental shelf

Produced water (PW), a large byproduct of offshore oil and gas extraction, is reinjected to formations or discharged to the sea after treatment. The discharges contain dispersed crude oil, polycyclic aromatic hydrocarbons (PAHs), alkylphenols (APs), metals, and many other constituents of environmental relevance. Risk-based regulation, greener offshore chemicals and improved cleaning systems have reduced environmental risks of PW discharges, but PW is still the largest operational source of oil pollution to the sea from the offshore petroleum industry. Monitoring surveys find detectable exposures in caged mussel and fish several km downstream from PW outfalls, but biomarkers indicate only mild acute effects in these sentinels. On the other hand, increased concentrations of DNA adducts are found repeatedly in benthic fish populations, especially in haddock. It is uncertain whether increased adducts could be a long-term effect of sediment contamination due to ongoing PW discharges, or earlier discharges of oil-containing drilling waste. Another concern is uncertainty regarding the possible effect of PW discharges in the sub-Arctic Southern Barents Sea. So far, research suggests that sub-arctic species are largely comparable to temperate species in their sensitivity to PW exposure. Larval deformities and cardiac toxicity in fish early life stages are among the biomarkers and adverse outcome pathways that currently receive much attention in PW effect research. Herein, we summarize the accumulated ecotoxicological knowledge of offshore PW discharges and highlight some key remaining knowledge needs.

Environmental impacts of produced water and drilling waste discharges from the Norwegian offshore petroleum industry

Operational discharges of produced water and drill cuttings from offshore oil and gas platforms are a continuous source of contaminants to continental shelf ecosystems. This paper reviews recent research on the biological effects of such discharges with focus on the Norwegian Continental Shelf. The greatest concern is linked to effects of produced water. Alkylphenols (AP) and polyaromatic hydrocarbons (PAH) from produced water accumulate in cod and blue mussel caged near outlets, but are rapidly metabolized in cod. APs, naphtenic acids, and PAHs may disturb reproductive functions, and affect several chemical, biochemical and genetic biomarkers. Toxic concentrations seem restricted to <2 km distance. At the peak of discharge of oil-contaminated cuttings fauna disturbance was found at more than 5 km from some platforms, but is now seldom detected beyond 500 m. Water-based cuttings may seriously affect biomarkers in filter feeding bivalves, and cause elevated sediment oxygen consumption and mortality in benthic fauna. Effects levels occur within 0.5-1 km distance. The stress is mainly physical. The risk of widespread, long term impact from the operational discharges on populations and the ecosystem is presently considered low, but this cannot be verified from the published literature.

Environmental risk assessment of alkylphenols from offshore produced water on fish reproduction

Concern has been raised over whether environmental release of alkylphenols (AP) in produced water (PW) discharges from the offshore oil industry could impose a risk to the reproduction of fish stocks in the North Sea. An environmental risk assessment (ERA) was performed to determine if environmental exposure to PW APs in North Sea fish populations is likely to be high enough to give effects on reproduction endpoints. The DREAM (Dose related Risk and Effect Assessment Model) software was used in the study and the inputs to the ERA model included PW discharge data, fate information of PW plumes, fish distribution information, as well as uptake and elimination information of PW APs. Toxicodynamic data from effect studies with Atlantic cod (Gadus morhua) exposed to APs were used to establish a conservative environmental risk threshold value for AP concentration in seawater. By using the DREAM software to 1) identify the areas of highest potential risk and 2) integrate fish movement and uptake/elimination rates of APs for the chosen areas we found that the environmental exposure of fish to APs from PW is most likely too low to affect reproduction in wild populations of fish in the North Sea. The implications related to risk management of offshore PW and uncertainties in the risk assessment performed are discussed.

Biomarkers in natural fish populations indicate adverse biological effects of offshore oil production

Background

Despite the growing awareness of the necessity of a sustainable development, the global economy continues to depend largely on the consumption of non-renewable energy resources. One such energy resource is fossil oil extracted from the seabed at offshore oil platforms. This type of oil production causes continuous environmental pollution from drilling waste, discharge of large amounts of produced water, and accidental spills.

Methods and principal findings

Samples from natural populations of haddock (Melanogrammus aeglefinus) and Atlantic cod (Gadus morhua) in two North Sea areas with extensive oil production were investigated. Exposure to and uptake of polycyclic aromatic hydrocarbons (PAHs) were demonstrated, and biomarker analyses revealed adverse biological effects, including induction of biotransformation enzymes, oxidative stress, altered fatty acid composition, and genotoxicity. Genotoxicity was reflected by a hepatic DNA adduct pattern typical for exposure to a mixture of PAHs. Control material was collected from a North Sea area without oil production and from remote Icelandic waters. The difference between the two control areas indicates significant background pollution in the North Sea.

Conclusion

It is most remarkable to obtain biomarker responses in natural fish populations in the open sea that are similar to the biomarker responses in fish from highly polluted areas close to a point source. Risk assessment of various threats to the marine fish populations in the North Sea, such as overfishing, global warming, and eutrophication, should also take into account the ecologically relevant impact of offshore oil production.

Repeated sampling of Atlantic cod (Gadus morhua) for monitoring of nondestructive parameters during exposure to a synthetic produced water

The past decades of monitoring discharges from oil and gas industry have revealed that although there are indications of adverse effects in tissues of aquatic organisms, little is known about their temporal development. Furthermore, observations in wild-caught individuals have not been clearly reproduced in laboratory studies or caging studies, and vice versa, and the results are therefore not easily interpretable. There is clearly a need for exposure studies designed for monitoring the development of effect markers in individual fish over chronic periods to low contaminant levels. Through repetitive nondestructive sampling, the progression of effects may be monitored in individuals, significantly reducing the number of fish needed in exposure studies. A laboratory exposure study was designed to be able to monitor selected parameters in individual Atlantic cod (Gadus morhua). Passive integrated transponders in combination with visible implant elastomers were used to study individual fish during the exposure period (44 wk). Fish were measured (weight and length) and a blood sample was taken for analysis of hematocrit, DNA damage (micronucleus), and oxidative stress (total oxyradical scavenging capacity) at up to seven time points. There were no apparent adverse effects of treatments on the health of experimental fish, frequency of micronucleated erythrocytes, or oxidative stress in whole blood. It is possible that the time scale was not sufficient for development and detection of parameters included here or that red blood cells may not be a suitable matrix for the selected analyses. Future studies need to include other parameters in blood to investigate their sensitivity to low-concentration exposures.

Biomarker candidate discovery in Atlantic cod (Gadus morhua) continuously exposed to North Sea produced water from egg to fry

In this study Atlantic cod (Gadus morhua) were exposed to different levels of North Sea produced water (PW) and 17beta-oestradiol (E(2)), a natural oestrogen, from egg to fry stage (90 days). By comparing changes in protein expression following E(2) exposure to changes induced by PW treatment, we were able to compare the induced changes by PW to the mode of action of oestrogens. Changes in the proteome in response to exposure in whole cod fry (approximately 80 days post-hatching, dph) were detected by two-dimensional gel electrophoresis and image analysis and identified by MALDI-ToF-ToF mass spectrometry, using a newly developed cod EST database and the NCBI database. Many of the protein changes occurred at low levels (0.01% and 0.1% PW) of exposure, indicating putative biological responses at lower levels than previously detected. Using discriminant analysis, we identified a set of protein changes that may be useful as biomarker candidates of produced water (PW) and oestradiol exposure in Atlantic cod fry. The biomarker candidates discovered in this study may, following validation, prove effective as diagnostic tools in monitoring exposure and effects of discharges from the petroleum industry offshore, aiding future environmental risk analysis and risk management.

Development of a laboratory exposure system using marine fish to carry out realistic effect studies with produced water discharged from offshore oil production

A biotest system for environmentally realistic exposure of fish to produced water (PW) was developed and tested. Authentic PW was collected at an oil production platform in the North Sea and preserved by freezing in multiple aliquots a 25L. After transport to the test laboratory onshore, daily PW aliquots were thawed, homogenised and administered to the test fish, Atlantic cod (Gadus morhua), in two diluted exposure concentrations, 0.1% and 0.5%, during a 15 d period, using a continuous flow-through exposure setup. Positive control groups were exposed to two crude oil treatments for comparison. Chemical analyses showed that alkylphenol (AP) and PAH concentrations in PW exposure waters were very low. Observations of significantly increased AP and PAH metabolite levels in PW exposed fish demonstrated the suitability of the biotest system for its use in biological exposure/effect studies of PW, and it also demonstrated the sensitivity of bile metabolites as PW exposure markers in fish. The relevance of the biotest system for PW effect studies and for validating modelled environmental risk estimates of PW dischargers from offshore oil production is discussed.

Uptake and tissue distribution of C4-C7 alkylphenols in Atlantic cod (Gadus morhua): relevance for biomonitoring of produced water discharges from oil production

The sensitivity of different tissues for assessment of chronic low-dose environmental exposure of fish to alkylphenols (APs) was investigated. We exposed Atlantic cod (Gadus morhua) in the laboratory to tritium labelled 4-tert-butylphenol, 4n-pentylphenol, 4n-hexylphenol, and 4n-heptylphenol via seawater (8 ng/l) and via contaminated feed (5 microg/kg fish per day). Measurements of different fish tissues during eight days of exposure and eight subsequent days of recovery revealed that APs administered via spiked seawater were readily taken up whereas the uptake was far less efficient when APs were administered in spiked feed. AP residues were mainly located in the bile fluid whereas the concentrations in liver were very low, indicating a rapid excretion and the liver-bile axis to be the major route of elimination. The biological half-life of APs in the exposed cod was short, between 10 and 20 h. Our study shows that in connection with biomonitoring of AP exposure in fish, assessment of AP metabolites in bile fluid is a more sensitive tool than detection of parent AP levels in liver or other internal tissues.

Androgenic modulation of early growth of Atlantic cod (Gadus morhua L.) previtellogenic oocytes and zona radiata-related genes

Available evidence suggests that androgens play critical roles in early oocyte growth and development in fish. However, the molecular mechanisms underlying this important aspect of reproductive endocrinology have not yet been established. In this study the effects of androgens (11-ketotestosterone [11-KT] and testosterone [T]) were determined on gene expression patterns and growth of cod previtellogenic oocytes, using an in vitro oocyte culture technique. Previtellogenic ovarian tissue was cultured for 5 and 10 d at different concentrations of 11-KT and T (0, 1, or 1000 microM) dissolved in ethanol (0.3%). The androgen concentrations were selected as they represent physiological and supra-physiological concentrations, respectively. Quantitative polymerase chain reaction (PCR) demonstrated increased mRNA expression for five genes recently identified as androgen responsive in our subtracted cDNA library in previtellogenic cod ovary exposed in vitro to androgens. Quantitative histological analyses showed a consistent stereological validation of oocyte growth and development after exposure to androgens. In general, both 11-KT and T induced previtellogenic oocyte growth and development, and these effects were more pronounced with 11-KT exposure. Taken together, our study reveals some novel roles of androgens on the development of previtellogenic oocytes, indicating control of early follicular and oocyte growth in cod ovary. The potent effects of 11-KT on oocyte growth support our earlier hypothesis that non-aromatizable androgens play significant roles in regulating early oocyte growth with potential consequences for the fecundity process. Therefore, these novel roles of androgens as promoters of ovarian growth and development presented in this study may be useful for the aquaculture industry and for breeding of new captive and endangered species. From a toxicological point of view, the cod is a marine species and exposure to complex chemical mixtures that may exert androgenic and/or anti-androgenic effects represents an environmental issue of reasonable concern in the marine environment. Therefore, the findings in the present study represent a novel basis that can be used to determine the effects of xenoandrogens on oocyte development and fecundity in this important marine species.