Phospholipase PLA2G7 is complementary to GPX4 in mitigating punicic-acid-induced ferroptosis in prostate cancer cells.

Ferroptosis is a cell death pathway that can be promoted by peroxidizable polyunsaturated fatty acids in cancer cells. Here, we investigated the mechanisms underlying the toxicity of punicic acid (PunA), an isomer of conjugated linolenic acids (CLnAs) bearing three conjugated double bonds highly prone to peroxidation, on prostate cancer (PCa) cells. PunA induced ferroptosis in PCa cells and triggered massive lipidome remodeling, more strongly in PC3 androgen-negative cells than in androgen-positive cells. The greater sensitivity of androgen-negative cells to PunA was associated with lower expression of glutathione peroxidase 4 (GPX4). We then identified the phospholipase PLA2G7 as a PunA-induced ferroptosis suppressor in PCa cells. Overexpressing PLA2G7 decreased lipid peroxidation levels, suggesting that PLA2G7 hydrolyzes hydroperoxide-containing phospholipids, thus preventing ferroptosis. Importantly, overexpressing both PLA2G7 and GPX4 strongly prevented PunA-induced ferroptosis in androgen-negative PCa cells. This study shows that PLA2G7 acts complementary to GPX4 to protect PCa cells from CLnA-induced ferroptosis.

Terrestrial Birth and Body Size Tune UCP1 Functionality in Seals.

The molecular evolution of the mammalian heater protein UCP1 is a powerful biomarker to understand thermoregulatory strategies during species radiation into extreme climates, such as aquatic life with high thermal conductivity. While fully aquatic mammals lost UCP1, most semiaquatic seals display intact UCP1 genes, apart from large elephant seals. Here, we show that UCP1 thermogenic activity of the small-bodied harbor seal is equally potent compared to terrestrial orthologs, emphasizing its importance for neonatal survival on land. In contrast, elephant seal UCP1 does not display thermogenic activity, not even when translating a repaired or a recently highlighted truncated version. Thus, the thermogenic benefits for neonatal survival during terrestrial birth in semiaquatic pinnipeds maintained evolutionary selection pressure on UCP1 function and were only outweighed by extreme body sizes among elephant seals, fully eliminating UCP1-dependent thermogenesis.

Dynamics of leaching of POPs and additives from plastic in a Procellariiform gastric model: Diet- and polymer-dependent effects and implications for long-term exposure.

Procellariiform seabirds are known to have high rates of plastic ingestion. We investigated the bioaccessibility of plastic-associated chemicals [plastic additives and sorbed persistent organic pollutants (POPs)] leached from plastic over time using an in vitro Procellariiform gastric model. High-density polyethylene (HDPE) and polyvinyl chloride (PVC), commonly ingested by Procellariiform seabirds, were manufactured with one additive [decabrominated diphenyl ether (PBDE-209) or bisphenol S (BPS)]. HDPE and PVC added with PBDE-209 were additionally incubated in salt water with 2,4,4'-trichloro-1,1'-biphenyl (PCB-28) and 2,2',3,4,4',5'-hexachlorobiphenyl (PCB-138) to simulate sorption of POPs on plastic in the marine environment. Our results indicate that the type of plastic (nature of polymer and additive), presence of food (i.e., lipids and proteins) and gastric secretions (i.e., pepsin) influence the leaching of chemicals in a seabird. In addition, 100% of the sorbed POPs were leached from the plastic within 100 hours, while only 2-5% of the additives were leached from the matrix within 100 hours, suggesting that the remaining 95% of the additives could continue to be leached. Overall, our study illustrates how plastic type, diet and plastic retention time can influence a Procellariform's exposure risk to plastic-associated chemicals.

Foraging behavior and age affect maternal transfer of mercury to northern elephant seal pups.

Deep ocean foraging northern elephant seals (Mirounga angustirostris) consume fish and squid in remote depths of the North Pacific Ocean. Contaminants bioaccumulated from prey are subsequently transferred by adult females to pups during gestation and lactation, linking pups to mercury contamination in mesopelagic food webs (200-1000 m depths). Maternal transfer of mercury to developing seal pups was related to maternal mercury contamination and was strongly correlated with maternal foraging behavior (biotelemetry and isotopes). Mercury concentrations in lanugo (hair grown in utero) were among the highest observed worldwide for young pinnipeds (geometric mean 23.01 µg/g dw, range 8.03-63.09 µg/g dw; n = 373); thus, some pups may be at an elevated risk of sub-lethal adverse health effects. Fetal mercury exposure was affected by maternal foraging geographic location and depth; mercury concentrations were highest in pups of the deepest diving, pelagic females. Moreover, pup lanugo mercury concentrations were strongly repeatable among successive pups of individual females, demonstrating relative consistency in pup mercury exposure based on maternal foraging strategies. Northern elephant seals are biosentinels of a remote deep-sea ecosystem. Our results suggest that mercury within North Pacific mesopelagic food webs may also pose an elevated risk to other mesopelagic-foraging predators and their offspring.

Dietary methylmercury and fatty acids affect the lipid metabolism of adipose tissue and liver in rainbow trout.

Methylmercury (MeHg) is a pervasive environmental contaminant in aquatic ecosystems that can reach elevated concentrations in fish of high trophic levels, such as salmonids. The present study aims at investigating the individual and combined impacts of dietary MeHg and fatty acids on lipid metabolism in juvenile rainbow trout (Oncorhynchus mykiss) with a focus on two key organs, adipose tissue and liver. MeHg and fatty acids are both known to act on energy homeostasis although little is known about their interplay on lipid metabolism in fish. Fish were fed diets enriched in linoleic acid (LA, 18:2 n-6), α-linolenic acid (ALA, 18:3 n-3), eicosapentaenoic acid (EPA, 20:5 n-3) or docosahexaenoic acid (DHA, 22:6 n-3) for ten weeks, with the addition of MeHg to the diets during the last six weeks (0, 2.4 or 5.5 mg MeHg/kg dry matter). LA and ALA are polyunsaturated fatty acids (PUFA) typical of plant-derived oils whereas EPA and DHA are n-3 long chain PUFA largely found in fish oil, all used in feed formulation in aquaculture. The results showed that the LA-enriched diet induced a higher whole-body lipid content compared to the three other diets. On the contrary, the addition of MeHg led to a significant reduction of the whole-body lipid content, regardless of the diet. Interestingly, the adipocytes were larger both in presence of LA, compared to EPA and DHA, or MeHg, indicating a lipogenic effect of these two compounds. No effect was, however, observed on lipid accumulation per gram of adipose tissue. The fatty acid composition of adipose tissue and liver was significantly modified by the dietary lipids, reflecting both the fatty acid composition of the diets and the high bioconversion capacity of the rainbow trout. Exposure to MeHg selectively led to a release of n-6 PUFA from the hepatic membranes of fish fed the LA-enriched diet, showing a disruption of the pathways using n-6 PUFA. This study highlights the significant impact of MeHg exposure and dietary fatty acids on lipid metabolism in fish. Further investigation is needed to elucidate the underlying mechanisms and to explore the potential involvement of other organs.

Effects of cortisol, epinephrine, and bisphenol contaminants on the transcriptional landscape of marine mammal blubber.

Top ocean predators such as marine mammals are threatened by intensifying anthropogenic activity, and understanding the combined effects of multiple stressors on their physiology is critical for conservation efforts. We investigated potential interactions between stress hormones and bisphenol contaminants in a model marine mammal, the northern elephant seal (NES). We exposed precision-cut adipose tissue slices (PCATS) from blubber of weaned NES pups to cortisol (CORT), epinephrine (EPI), bisphenol A (BPA), bisphenol S (BPS), or their combinations (CORT-EPI, BPA-EPI, and BPS-EPI) ex vivo and identified hundreds of genes that were differentially regulated in response to these treatments. CORT altered expression of genes associated with lipolysis and adipogenesis, whereas EPI and CORT-EPI-regulated genes were associated with responses to hormones, lipid and protein turnover, immune function, and transcriptional and epigenetic regulation of gene expression, suggesting that EPI has wide-ranging and prolonged impacts on the transcriptional landscape and function of blubber. Bisphenol treatments alone had a weak impact on gene expression compared with stress hormones. However, the combination of EPI with bisphenols altered expression of genes associated with inflammation, cell stress, DNA damage, regulation of nuclear hormone receptor activity, cell cycle, mitochondrial function, primary ciliogenesis, and lipid metabolism in blubber. Our results suggest that CORT, EPI, bisphenols, and their combinations impact cellular, immune, and metabolic homeostasis in marine mammal blubber, which may affect the ability of marine mammals to sustain prolonged fasting during reproduction and migration, renew tissues, and mount appropriate responses to immune challenges and additional stressors.

The Catechins Profile of Green Tea Extracts Affects the Antioxidant Activity and Degradation of Catechins in DHA-Rich Oil.

This study investigated the effect of the catechins profile on the antioxidant activity of green tea extracts (GTEs) by comparing the antioxidant activity of an EGC-rich GTE (GTE1, catechin content: 58% EGC, 30.1% EGCG, 7.9% EC, and 3.9% ECG) and an EGCG-rich GTE (GTE2, catechin content: 60.6% EGCG, 17.7% EGC, 11.8% ECG, and 9.8% EC) in a DHA-rich oil. The effects of the individual catechins (EGC, EC, EGCG, and ECG) and reconstituted catechins mixtures (CatMix), prepared to contain the same amount of major catechins as in the GTEs, were also measured. All treatments (GTE1, CatMix1, GTE2, CatMix2, EGC250, EC250, EGCG250, and ECG250), each containing epistructured catechins at a concentration of 250 ppm, as well as the control (oil with no added antioxidant), were stored at 30 °C for 21 days with sampling intervals of 7 days. The antioxidant activity was assessed by measuring the peroxide value (PV) and p-anisidine value (p-AV) of oils. Changes in fatty acid content and catechins content were also monitored. Both GTEs enhanced the oxidative stability of the DHA-rich oil, but GTE1 demonstrated a stronger antioxidant activity than GTE2. No significant difference was observed between the PV of treatments with GTE1 and CatMix1 during storage, whereas the PV of oil with GTE2 was significantly higher than that with CatMix2 after 21 days. Among the individual catechins, EGC was the strongest antioxidant. Overall, the antioxidant activities of the extracts and catechins were observed in the decreasing order GTE1 ≈ EGC250 ≈ CatMix1 > GTE2 > EGCG250 ≈ CatMix2 > ECG250 > EC250. A significant change in fatty acid content was observed for the control and EC250 samples, and the catechins were most stable in GTE1-supplemented oil. Our results indicate that the EGC-rich GTE is a more potent antioxidant in DHA-rich oil than the EGCG-rich GTE.

Punicic Acid Triggers Ferroptotic Cell Death in Carcinoma Cells.

Plant-derived conjugated linolenic acids (CLnA) have been widely studied for their preventive and therapeutic properties against diverse diseases such as cancer. In particular, punicic acid (PunA), a conjugated linolenic acid isomer (C18:3 c9t11c13) present at up to 83% in pomegranate seed oil, has been shown to exert anti-cancer effects, although the mechanism behind its cytotoxicity remains unclear. Ferroptosis, a cell death triggered by an overwhelming accumulation of lipid peroxides, has recently arisen as a potential mechanism underlying CLnA cytotoxicity. In the present study, we show that PunA is highly cytotoxic to HCT-116 colorectal and FaDu hypopharyngeal carcinoma cells grown either in monolayers or as three-dimensional spheroids. Moreover, our data indicate that PunA triggers ferroptosis in carcinoma cells. It induces significant lipid peroxidation and its effects are prevented by the addition of ferroptosis inhibitors. A combination with docosahexaenoic acid (DHA), a known polyunsaturated fatty acid with anticancer properties, synergistically increases PunA cytotoxicity. Our findings highlight the potential of using PunA as a ferroptosis-sensitizing phytochemical for the prevention and treatment of cancer.

Predicting consequences of POP-induced disruption of blubber glucose uptake, mass gain rate and thyroid hormone levels for weaning mass in grey seal pups.

Persistent organic pollutants (POPs) are endocrine disruptors that alter adipose tissue development, regulation and function. Top marine predators are particularly vulnerable because they possess large fat stores that accumulate POPs. However, links between endocrine or adipose tissue function disruption and whole animal energetics have rarely been investigated. We predicted the impact of alterations to blubber metabolic characteristics and circulating thyroid hormone (TH) levels associated with polychlorinated biphenyls (PCBs), polybrominated diphenyl ethers (PBDEs), and organochlorine pesticides (OCPs) on suckling mass gain and weaning mass in wild grey seal pups. Glucose uptake by inner blubber was a strong predictor of whole animal mass gain rate, which in turn, resulted in heavier weaning mass. Weaning mass was predicted to increase by 3.7 ± 1.59 (sem) %, through increased mass gain rate, in the absence of the previously reported suppressive effect of dioxin-like PCB (DL-PCBs) on blubber glucose uptake. PBDEs were, conversely, associated with faster mass gain. Alleviation of this effect was predicted to reduce weaning mass by 6.02 ± 1.86% (sem). To better predict POPs effects on energy balance, it is crucial to determine if and how PBDEs promote mass gain in grey seal pups. Weaning mass was negatively related to total T3 (TT3) levels. A 20% (range = 9.3-31.7%) reduction in TT3 by DL-PCBs partially overcame the effect of DL-PCB -mediated reduction in blubber glucose uptake. Overall, DL-PCBs were thus predicted to reduce weaning mass by 1.86 ± 1.60%. Organohalogen impacts on whole-animal energy balance in grey seal pups appear to partially offset each other through opposing effects on different mechanisms. POP effects were generally minor, but the largest POP-induced reductions in weaning mass were predicted to occur in pups that were already small. Since weaning mass is positively related to first-year survival, POPs may disproportionately affect smaller individuals, and could continue to have population-level impacts even when levels are relatively low compared to historical values. Our findings show how in vitro experiments combined with measurements in vivo can help elucidate mechanisms that underpin energy balance regulation and help to quantify the magnitude of disruptive effects by contaminants and other stressors in wildlife.

Methylmercury displays pro-adipogenic properties in rainbow trout preadipocytes.

Methylmercury (MeHg) is a ubiquitous contaminant largely found in aquatic environments, especially in species at high trophic level such as salmonids. The aim of this study was to evaluate the effects of MeHg on adipocyte differentiation and lipid metabolism in rainbow trout. Primary cultured preadipocytes were exposed to increasing concentrations of MeHg during six days with or without a hormonal cocktail. Main results showed a dose-dependent intracellular accumulation of neutral lipids with a preferential uptake of n-3 polyunsaturated fatty acids. Interestingly, this accumulation occurred after a fairly low uptake of MeHg by preadipocytes and was maintained after the cellular exposure to MeHg. In membrane phospholipids, arachidonic acid (20:4 n-6) was released in a dose-dependent manner. At the transcriptional level, the expression of several adipocyte-specific genes (perilipin 2 and apolipoprotein Eb) as well as lipid-related genes (fatty acid synthase and fatty acid binding protein 11a) was up-regulated in preadipocytes exposed to MeHg. These results highlight for the first time the disrupting effect of MeHg in trout adipocyte metabolism, providing new insights regarding the role of environmental pollutants in adipose tissue dysfunction and related pathologies.

Interplay between dietary lipids and cadmium exposure in rainbow trout liver: Influence on fatty acid metabolism, metal accumulation and stress response.

The present study aimed at investigating interactive effects between dietary lipids and both short- and long-term exposures to a low, environmentally realistic, cadmium (Cd) concentration. Juvenile rainbow trout were fed four isolipidic diets (31.7 g/kg) enriched in either linoleic acid (LA, 18:2n-6), alpha-linolenic acid (ALA, 18:3n-3), eicosapentaenoic acid (EPA, 20:5n-3) or docosahexaenoic acid (DHA, 22:6n-3). From the 4th week of this 10-week experiment, the lipid level of the diet was increased (120.0 g/kg) and half of the fish fed each diet were aqueously exposed to Cd (0.3 µg/L) while the other half were not exposed to Cd (control). Fish were sampled and their liver was harvested for fatty acid profile, hepatic Cd and calcium concentrations, total glutathione level and gene expression assessment, either (i) after 4 weeks of feeding and 24 h of Cd contamination (day 29) (short-term Cd exposure) or (ii) after 10 weeks of feeding and 6 weeks of Cd contamination (day 70) (long-term Cd exposure). We found that both dietary lipids and Cd exposure influenced fatty acid homeostasis and metabolism. The hepatic fatty acid profile mostly reflected that of the diet (e.g. n-3/n-6 ratio) with some differences, including selective retention of specific long chain polyunsaturated fatty acids (LC-PUFAs) like DHA and active biotransformation of dietary LA and ALA into LC-PUFAs. Cd effects on hepatic fatty acid profiles were influenced by the duration of the exposure and the nutritional status of the fish. The effects of diet and Cd exposure on the fatty acid profiles were only sparsely explained by variation of the expression pattern of genes involved in fatty acid metabolism. The biological responses to Cd were also influenced by dietary lipids. Fish fed the ALA-enriched diet seemed to be the least affected by the Cd exposure, as they showed a higher detoxifying ability against Cd with an early upregulation of protective metallothionein a (MTa) and apoptosis regulator BCL2-Like1 (BCLx) genes, an increased long-term phospholipid synthesis and turnover and fatty acid bioconversion efficiency, as well as a lower long-term accumulation of Cd in their liver. In contrast, fish fed the EPA-enriched diet seemed to be the most sensitive to a long-term Cd exposure, with an impaired growth performance and a decreased antioxidant capacity (lower glutathione level). Our results highlight that low, environmentally realistic aqueous concentrations of Cd can affect biological response in fish and that these effects are influenced by the dietary fatty acid composition.

In vitro Lipolysis and Leptin Production of Elephant Seal Blubber Using Precision-Cut Adipose Tissue Slices.

Adipose tissue plays key roles in energy homeostasis. Understanding its metabolism and regulation is essential to predict the impact of environmental changes on wildlife health, especially in fasting-adapted species. However, in vivo experimental work in wild vertebrates can be challenging. We have developed a novel in vitro approach of precision-cut adipose tissue slices from northern elephant seal (Mirounga angustirostris) as a complementary approach to whole animal models. Blubber biopsies were collected from 14 pups during early and late post-weaning fast (Año Nuevo, CA, United States), precision-cut into 1 mm thick slices and maintained in culture at 37°C for at least 63 h. The slices exhibited an efficient response to ß-adrenergic stimulation, even after 2 days of culture, revealing good in vitro tissue function. The response to lipolytic stimulus did not vary between regions of outer and inner blubber, but was higher at early than at late fast for inner blubber slices. At early fast, lipolysis significantly reduced leptin production. At this stage, inner blubber slices were also more efficient at producing leptin than outer blubber slices, especially in the non-lipolytic condition. This model will aid the study of adipose tissue metabolism and its response to environmental stressors in marine mammals.

Exploring the interactions between polyunsaturated fatty acids and cadmium in rainbow trout liver cells: a genetic and proteomic study.

Polyunsaturated fatty acids (PUFAs) have key biological roles in fish cells. We recently showed that the phospholipid composition of rainbow trout liver cells (RTL-W1 cell line) modulates their tolerance to an acute cadmium (Cd) challenge. Here, we investigated (i) the extent to which PUFAs and Cd impact fatty acid homeostasis and metabolism in these cells and (ii) possible mechanisms by which specific PUFAs may confer cytoprotection against Cd. First, RTL-W1 cells were cultivated for one week in growth media spiked with 50 µmol L-1 of either alpha-linolenic acid (ALA, 18:3n-3), eicosapentaenoic acid (EPA, 20:5n-3), linoleic acid (LA, 18:2n-6) or arachidonic acid (AA, 20:4n-6) in order to modulate their fatty acid profile. Then, the cells were challenged with Cd (0, 50 or 100 µmol L-1) for 24 h prior to assaying viability, fatty acid profile, intracellular Cd content, proteomic landscape and expression levels of genes involved in fatty acid metabolism, synthesis of PUFA-derived signalling molecules and stress response. We observed that the fatty acid supply and, to a lesser extent, the exposure to Cd influenced cellular fatty acid homeostasis and metabolism. The cellular fatty acid composition of fish liver cells modulated their tolerance to an acute Cd challenge. Enrichments in ALA, EPA, and, to a lesser extent, AA conferred cytoprotection while enrichment in LA had no impact on cell viability. The present study ruled out the possibility that cytoprotection reflects a decreased Cd burden. Our results rather suggest that the PUFA-derived cytoprotection against Cd occurs through a reduction of the oxidative stress induced by Cd and a differential induction of the eicosanoid cascade, with a possible role of peroxiredoxin and glutaredoxin (antioxidant enzymes) as well as cytosolic phospholipase A2 (enzyme initiating the eicosanoid cascade).

Persistent Organic Pollutant Burden, Experimental POP Exposure, and Tissue Properties Affect Metabolic Profiles of Blubber from Gray Seal Pups.

Persistent organic pollutants (POPs) are toxic, ubiquitous, resist breakdown, bioaccumulate in living tissue, and biomagnify in food webs. POPs can also alter energy balance in humans and wildlife. Marine mammals experience high POP concentrations, but consequences for their tissue metabolic characteristics are unknown. We used blubber explants from wild, gray seal ( Halichoerus grypus) pups to examine impacts of intrinsic tissue POP burden and acute experimental POP exposure on adipose metabolic characteristics. Glucose use, lactate production, and lipolytic rate differed between matched inner and outer blubber explants from the same individuals and between feeding and natural fasting. Glucose use decreased with blubber dioxin-like PCBs (DL-PCB) and increased with acute experimental POP exposure. Lactate production increased with DL-PCBs during feeding, but decreased with DL-PCBs during fasting. Lipolytic rate increased with blubber dichlorodiphenyltrichloroethane and its metabolites (DDX) in fasting animals, but declined with DDX when animals were feeding. Our data show that POP burdens are high enough in seal pups to alter adipose function early in life, when fat deposition and mobilization are vital. Such POP-induced alterations to adipose metabolic properties may significantly alter energy balance regulation in marine top predators, with the potential for long-term impacts on fitness and survival.

Transcriptional effects of phospholipid fatty acid profile on rainbow trout liver cells exposed to methylmercury.

Lipids, and their constitutive fatty acids, are key nutrients for fish health as they provide energy, maintain cell structure, are precursors of signalling molecules and act as nuclear receptor ligands. These specific roles may be of crucial importance in a context of exposure to pollutants. We recently showed that the fatty acid profile of rainbow trout liver cell phospholipids modulates sensitivity to an acute methylmercury challenge. In order to investigate mechanisms of effects, we herein tested whether specific polyunsaturated fatty acids (PUFAs) may protect cells from methylmercury through decreasing intracellular mercury accumulation and/or enhancing cellular defences (e.g. via modulation of gene expression patterns). We also investigated the inverse relationship and assessed the impact of methylmercury on cellular fatty acid metabolism. To do so, the fatty acid composition of rainbow trout liver cell phospholipids was first modified by incubating them in a medium enriched in a specific PUFA from either the n-3 family (alpha-linolenic acid, ALA; eicosapentaenoic acid, EPA) or the n-6 family (linoleic acid, LA; arachidonic acid, AA). Cells were then exposed to methylmercury (0.15 or 0.50 µM) for 24 h and sampled thereafter for assessing phospholipid fatty acid profile, intracellular total mercury burden, and expression pattern of genes involved in fatty acid metabolism, synthesis of PUFA-derived signalling molecules and stress response. We observed that cells incorporated the given PUFA and some biotransformation products in their phospholipids. Methylmercury had few impacts on this cellular phospholipid composition. None of the PUFA enrichments affected the cellular mercury burden, suggesting that the previously observed cytoprotection conferred by ALA and EPA was not linked to a global decrease in cellular accumulation of mercury. Fatty acid enrichments and methylmercury exposure both modulated gene expression patterns. Genes involved in the synthesis of PUFA-derived signalling molecules, in stress response and the orphan cytochrome P450 20A1 were identified as possible sites of interaction between fatty acids and methylmercury in rainbow trout liver cells.

Body lipid composition modulates acute cadmium toxicity in Daphnia magna adults and juveniles.

Long chain polyunsaturated fatty acids (LC-PUFAs) such as eicosapentaenoic acid (EPA, 20:5n-3) affect zooplankton fitness and ability to cope with environmental stressors. However, the impact of LC-PUFAs on zooplankton sensitivity to chemical stressors is unknown. Here, we aimed to document the interaction between EPA and cadmium (Cd), as model chemical stressor, in Daphnia magna. A life-history experiment was performed in which daphnid neonates were raised into adulthood on three diets of different lipid composition: (i) algae mix; (ii) algae mix supplemented with control liposomes; (iii) algae mix supplemented with liposomes containing EPA. Juveniles (3rd, 4th and 5th brood) released by daphnids during this life-history experiment were sampled, challenged with Cd during 48 h and their immobility was assessed. At the end of this life-history experiment, another immobilisation test was performed with adults from each treatment. Daphnids absorbed, incorporated and transferred ingested EPA to their offspring. Liposome feeding increased adult tolerance to Cd. The presence of EPA in liposomes did not increase adult tolerance to Cd. Offspring's tolerance to Cd was influenced by the brood number and the maternal diet. It was positively correlated with the PUFA level in body neutral lipids, especially alpha-linolenic acid (ALA, 18:3n-3) and negatively correlated with the saturated fatty acid level in body neutral lipids, especially stearic acid (18:0). Overall, these results emphasize the importance of dietary lipids and maternal transfer of body lipids in D. magna sensitivity to Cd and highlight the need to take into account these parameters in ecotoxicological studies and risk assessment.

Temperature Increase Negatively Affects the Fatty Acid Bioconversion Capacity of Rainbow Trout (Oncorhynchus mykiss) Fed a Linseed Oil-Based Diet.

Aquaculture is meant to provide fish rich in omega-3 long chain polyunsaturated fatty acids (n-3 LC-PUFA). This objective must be reached despite (1) the necessity to replace the finite and limited fish oil in feed production and (2) the increased temperature of the supply water induced by the global warming. The objective of the present paper was to determine to what extent increased water temperature influences the fatty acid bioconversion capacity of rainbow trout (Oncorhynchus mykiss) fed a plant-derived diet. Fish were fed two diets formulated with fish oil (FO) or linseed oil (LO) as only added lipid source at the optimal water temperature of 15°C or at the increased water temperature of 19°C for 60 days. We observed that a temperature increase close to the upper limit of the species temperature tolerance range negatively affected the feed efficiency of rainbow trout fed LO despite a higher feed intake. The negative impact of increased water temperature on fatty acid bioconversion capacity appeared also to be quite clear considering the reduced expression of fatty acid desaturase 2 in liver and intestine and the reduced Δ6 desaturase enzymatic activity in intestinal microsomes. The present results also highlighted a negative impact of increased temperature on the apparent in vivo enzymatic activity of Δ5 and Δ6 desaturases of fish fed LO. Interestingly, this last parameter appeared less affected than those mentioned above. This study highlights that the increased temperature that rainbow trout may face due to global warming could reduce their fatty acid bioconversion capacity. The unavoidable replacement of finite fish oil by more sustainable, readily available and economically viable alternative lipid sources in aquaculture feeds should take this undeniable environmental issue on aquaculture productivity into account.

Serum POP concentrations are highly predictive of inner blubber concentrations at two extremes of body condition in northern elephant seals.

Long-lived, upper trophic level marine mammals are vulnerable to bioaccumulation of persistent organic pollutants (POPs). Internal tissues may accumulate and mobilize POP compounds at different rates related to the body condition of the animal and the chemical characteristics of individual POP compounds; however, collection of samples from multiple tissues is a major challenge to ecotoxicology studies of free-ranging marine mammals and the ability to predict POP concentrations in one tissue from another tissue remains rare. Northern elephant seals (Mirounga angustirostris) forage on mesopelagic fish and squid for months at a time in the northeastern Pacific Ocean, interspersed with two periods of fasting on land, which results in dramatic seasonal fluctuations in body condition. Using northern elephant seals, we examined commonly studied tissues in mammalian toxicology to describe relationships and determine predictive equations among tissues for a suite of POP compounds, including ΣDDTs, ΣPCBs, Σchlordanes, and ΣPBDEs. We collected paired blubber (inner and outer) and blood serum samples from adult female and male seals in 2012 and 2013 at Año Nuevo State Reserve (California, USA). For females (N = 24), we sampled the same seals before (late in molting fast) and after (early in breeding fast) their approximately seven month foraging trip. For males, we sampled different seals before (N = 14) and after (N = 15) their approximately four month foraging trip. We observed strong relationships among tissues for many, but not all compounds. Serum POP concentrations were strong predictors of inner blubber POP concentrations for both females and males, while serum was a more consistent predictor of outer blubber for males than females. The ability to estimate POP blubber concentrations from serum, or vice versa, has the potential to enhance toxicological assessment and physiological modeling. Furthermore, predictive equations may illuminate commonalities or distinctions in bioaccumulation across marine mammal species.

The fatty acid profile of rainbow trout liver cells modulates their tolerance to methylmercury and cadmium.

The polyunsaturated fatty acid (PUFA) composition of fish tissues, which generally reflects that of the diet, affects various cellular properties such as membrane structure and fluidity, energy metabolism and susceptibility to oxidative stress. Since these cellular parameters can play an important role in the cellular response to organic and inorganic pollutants, a variation of the PUFA supply might modify the toxicity induced by such xenobiotics. In this work, we investigated whether the cellular fatty acid profile has an impact on the in vitro cell sensitivity to two environmental pollutants: methylmercury and cadmium. Firstly, the fatty acid composition of the rainbow trout liver cell line RTL-W1 was modified by enriching the growth medium with either alpha-linolenic acid (ALA, 18:3n-3), eicosapentaenoic acid (EPA, 20:5n-3), docosahexaenoic acid (DHA, 22:6n-3), linoleic acid (LA, 18:2n-6), arachidonic acid (AA, 20:4n-6) or docosapentaenoic acid (DPA, 22:5n-6). These modified cells and their control (no PUFA enrichment) were then challenged for 24h with increasing concentrations of methylmercury or cadmium. We observed that (i) the phospholipid composition of the RTL-W1 cells was profoundly modulated by changing the PUFA content of the growth medium: major modifications were a high incorporation of the supplemented PUFA in the cellular phospholipids, the appearance of direct elongation and desaturation metabolites in the cellular phospholipids as well as a change in the gross phospholipid composition (PUFA and monounsaturated fatty acid (MUFA) levels and n-3/n-6 ratio); (ii) ALA, EPA and DPA enrichment significantly protected the RTL-W1 cells against both methylmercury and cadmium; (iv) DHA enrichment significantly protected the cells against cadmium but not methylmercury; (v) AA and LA enrichment had no impact on the cell tolerance to both methylmercury and cadmium; (vi) the abundance of 20:3n-6, a metabolite of the n-6 biotransformation pathway, in phospholipids was negatively correlated to the cell tolerance to both methylmercury and cadmium. Overall, our results highlighted the importance of the fatty acid supply on the tolerance of fish liver cells to methylmercury and cadmium.