Primary hepatocytes from Arctic char (Salvelinus alpinus) as a relevant Arctic in vitro model for screening contaminants and environmental extracts

Profiling the Physiological Roles in Fish Primary Cell Culture

Fish primary cell culture has emerged as a valuable tool for investigating the physiological roles and responses of various cell types found in fish species. This review aims to provide an overview of the advancements and applications of fish primary cell culture techniques, focusing on the profiling of physiological roles exhibited by fish cells in vitro. Fish primary cell culture involves the isolation and cultivation of cells directly derived from fish tissues, maintaining their functional characteristics and enabling researchers to study their behavior and responses under controlled conditions. Over the years, significant progress has been made in optimizing the culture conditions, establishing standardized protocols, and improving the characterization techniques for fish primary cell cultures. The review highlights the diverse cell types that have been successfully cultured from different fish species, including gonad cells, pituitary cells, muscle cells, hepatocytes, kidney and immune cells, adipocyte cells and myeloid cells, brain cells, primary fin cells, gill cells, and other cells. Each cell type exhibits distinct physiological functions, contributing to vital processes such as metabolism, tissue regeneration, immune response, and toxin metabolism. Furthermore, this paper explores the pivotal role of fish primary cell culture in elucidating the mechanisms underlying various physiological processes. Researchers have utilized fish primary cell cultures to study the effects of environmental factors, toxins, pathogens, and pharmaceutical compounds on cellular functions, providing valuable insights into fish health, disease pathogenesis, and drug development. The paper also discusses the application of fish primary cell cultures in aquaculture research, particularly in investigating fish growth, nutrition, reproduction, and stress responses. By mimicking the in vivo conditions in vitro, primary cell culture has proven instrumental in identifying key factors influencing fish health and performance, thereby contributing to the development of sustainable aquaculture practices.

Suspended solids-associated toxicity of hydraulic fracturing flowback and produced water on early life stages of zebrafish (Danio rerio)

Hydraulic fracturing flowback and produced water (HF-FPW), which contains polyaromatic hydrocarbons (PAHs) and numerous other potential contaminants, is a complex wastewater produced during the recovery of tight hydrocarbon resources. Previous studies on HF-FPW have demonstrated various toxicological responses of aquatic organisms as consequences of combined exposure to high salinity, dissolved organic compounds and particle/suspended solids-bound pollutants. Noteworthy is the lack of studies illustrating the potentially toxic effects of the FPW suspended solids (FPW-SS). In this study, we investigated the acute and sublethal toxicity of suspended solids filtered from six authentic FPW sample collected from two fracturing wells, using a sediment contact assay based on early-life stages of zebrafish (Danio rerio). PAHs profiles and acute toxicity tests provided initial information on the toxic potency of the six samples. Upon exposure to sediment mixture at two selected doses (1.6 and 3.1 mg/mL), results showed adverse effects in larval zebrafish, as revealed by increased Ethoxyresorufin-O-deethylase (EROD) activity. Transcriptional alterations were also observed in xenobiotic biotransformation (ahr, pxr, cyp1a, cyp1b1, cyp1c1, cyp1c2, cyp3a65, udpgt1a1, udpgt5g1), antioxidant response (sod1, sod2, gpx1a, gpx1b) and hormone receptor signaling (esr1, esr2a, cyp19a1a, vtg1) genes. The results demonstrated that even separated from the complex aqueous FPW mixture, FPW-SS can induce toxicological responses in aquatic organisms' early life stages. Since FPW-SS could sediment to the bottom of natural wetland acting as a continuous source of contaminants, the current findings imply the likelihood of long-term environmental risks of polluted sediments on aquatic ecosystems due to FPW spills.

Marine Fish Primary Hepatocyte Isolation and Culture: New Insights to Enzymatic Dissociation Pancreatin Digestion

Primary cell cultures from wild organisms have been gaining relevance in ecotoxicology as they are considered more sensitive than immortalized cell lines and retain the biochemical pathways found in vivo. In this study, the efficacy of two methods for primary hepatocyte cell isolation was compared using liver from two marine fish (Sparus aurata and Psetta maxima): (i) two-step collagenase perfusion and (ii) pancreatin digestion with modifications. Cell cultures were incubated in L-15 medium at 17 ± 1 °C and monitored for up to six days for cell viability and function using the trypan blue exclusion test, MTT test, lactate dehydrogenase (LDH) activity, and ethoxyresorufin O-deethylase (EROD) activity after Benzo[a]Pyrene exposure. The results showed significant differences between the number of viable cells (p < 0.05), the highest number being obtained for the pancreatin digestion method (average = 4.5 ± 1.9 × 10⁷ cells). Moreover, the hepatocytes showed solid adherence to the culture plate and the rounded shape, changing into a triangular/polygonal shape. The cell viability and function obtained by pancreatin digestion were maintained for five days, and the EROD induction after exposure to the B[a]P showed that cells were metabolically active. This study shows that the optimized pancreatin digestion method is a valid, cost-effective, and simple alternative to the standard perfusion method for the isolation of primary hepatocytes from fish and is suitable for ecotoxicological studies involving marine pollutants, such as PAHs.

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.

A multi-site approach to investigate the role of toxicity and confounding factors on plant bioassay results

Development of organisms that live on contaminated soils depends on toxicity as well as several physical and chemical soil properties. We aimed to identify plant bioassays most responsive to contaminants and not to confounding factors due to soil type differences. We implemented a multi-site approach in seven contaminated sites and used different ordinary plant bioassays (fourteen-day-shoot biomass and five-day-root and shoot elongation). Most of the sites were contaminated with polycyclic aromatic hydrocarbons (PAHs), and soils were sampled from areas of both high and low contamination. Bioassays were performed on ninety soil samples and were carried out with six model species. We performed analyses of regulatory PAHs and their derivatives content in the samples. Fourteen-day-shoot biomass responses depended on the site's origin, with an intricate response of plants that faced contrasted soil pH and organic matter content and various contaminant levels. Five-day-shoot and root lengths were informative when considering the most heavily PAH-contaminated site, since both measures exhibited a close dose-dependent response to PAHs but not to soil pH or organic matter content. For the other sites, elongation tests revealed tenuous effects somehow related to the presence of PAHs or their derivatives. We propose that tests based on plant development during their autotrophic phase (the fourteen-day-shoot biomass test in this study) are likely more sensitive to environmental stressors but less specific for contaminant-induced effects. Comparatively, tests based on early and heterotrophic plant development could be particularly more specific for soil contaminants, but the associated responses may be of low sensitivity.

Metabolic signatures of bisphenol A and genistein in Atlantic salmon liver cells

Screening has revealed that aquafeeds with high inclusion of plant material may contain small amounts of endocrine disrupting agricultural pesticides. In this work, bisphenol A (BPA) and genistein (GEN) were selected as model endocrine disrupting toxicants with impact on DNA methylation in fish. Atlantic salmon hepatocytes were exposed in vitro to four concentrations of BPA and GEN (0.1, 1.0, 10 and 100 μM) for 48 h. Toxicity endpoints included cytotoxicity, global DNA methylation, targeted transcriptomics and metabolomic screening (100 μM). GEN was not cytotoxic in concentrations up to 100 μM, whereas one out of two cell viability assays indicated a cytotoxic response to 100 μM BPA. Compared to the control, significant global DNA hypomethylation was observed at 1.0 μM BPA. Both compounds upregulated cyp1a1 transcription at 100 μM, while estrogenic markers esr1 and vtg1 responded strongest at 10 μM. Dnmt3aa transcription was downregulated by both compounds at 100 μM. Metabolomic screening showed that BPA and GEN resulted in significant changes in numerous biochemical pathways consistent with alterations in carbohydrate metabolism, indicating perturbation in glucose homeostasis and energy generation, and glutamate metabolism. Pathway analysis showed that while the superpathway of methionine degradation was among the most strongly affected pathways by BPA, GEN induced changes to uridine and pyrimidine biosynthesis. In conclusion, this mechanistic study proposes metabolites associated with glucose and glutamate metabolism, glucuronidation detoxification, as well as cyp1a1, vtg1, esr1, ar, dnmt3aa, cdkn1b and insig1 as transcriptional markers for BPA and GEN exposure in fish liver cells.

Characterizing cytotoxic and estrogenic activity of Arctic char tissue extracts in primary Arctic char hepatocytes

Contaminants from various anthropogenic activities are detected in the Arctic due to long-range atmospheric transport, ocean currents, and living organisms such as migrating fish or seabirds. Although levels of persistent organic pollutants (POPs) in Arctic fish are generally low, local hot spots of contamination were found in freshwater systems such as Lake Ellasjøen at Bjørnøya (Bear Island, Norway). Higher concentrations of organic halogenated compounds (OHC), and higher levels of cytochrome P450 and DNA-double strand breaks were reported in Arctic char (Salvelinus alpinus) from this lake compared to fish from other lakes on Bjørnøya. Although several of the measured contaminants are potential endocrine disrupters, few studies have investigated potential endocrine disruptive effects of the contaminant cocktail in this fish population. The aim of this study was to compare acutely toxic and estrogenic potency of the cocktail of pollutants as evidenced by cytotoxic and/or estrogenic effects in vitro using extracts of Arctic char livers from contaminated Lake Ellasjøen with those from less contaminated Lake Laksvatn at Bjørnøya. This was performed by in situ sampling and contaminant extraction from liver tissue, followed by chemical analysis and in vitro testing of the following contaminated tissue extracts: F1-nonpolar OHC, F2-polar pesticides and metabolites of OHC, and F3-polar OHC. Contaminant levels were highest in extracts from Ellasjøen fish. The F2 and F3 extracts from Lake Laksvatn and Lake Ellasjøen fish reduced in vitro cell viability at a concentration ratio of 0.03-1 relative to tissue concentration in Arctic char. Only the F3 liver extract from Ellasjøen fish increased in vitro vitellogenin protein expression. Although compounds such as estrogenic OH-PCBs were quantified in Ellasjøen F3 extracts, it remains to be determined which compounds were inducing estrogenic effects.