Detoxification enzyme activities (CYP1A1 and GST) in the skin of humpback whales as a function of organochlorine burdens and migration status

Legacy and emerging contaminants in marine mammals from Argentina

Marine mammals are recognized sentinels of ecosystem health. They are susceptible to the accumulation and biomagnification of pollutants, which constitute one of the greatest threats to their survival. Legacy, such as organochlorine pesticides, and emerging contaminants, like microplastics and pharmaceuticals, may have effects on marine mammals' health at individual and population levels. Therefore, the evaluation of the risks associated with pollutants in this group is of great importance. The aim of this review is to provide information on the occurrence of legacy and emerging contaminants in marine mammals that inhabit Argentine waters. Also, to identify knowledge gaps and suggest best practices for future research. Reports of legacy contaminants referring to organochlorine pesticides and polychlorinated biphenyls were found in five species of cetaceans and two of pinnipeds. With respect to emerging pollutants, the presence of plastics was only evaluated in three species. Reported data was from at least a decade ago. Therefore, it is necessary to update existing information and conduct continuous monitoring to assess temporary trends in pollutants. All the studies were carried out in the province of Buenos Aires and Northern Patagonia indicating a knowledge gap in the southern zone of the Argentine Sea. In addition, pollutants of global environmental concern that have not been studied in Argentina are discussed. Future studies should fill these gaps and a greater effort to understand the relationships between pollutants and their effects on marine mammals is suggested. This issue will make it possible to determine thresholds for all the substances and species evaluated in order to carry out more detailed risk assessments and make decisions for the conservation of marine mammals in Argentine waters.

Immunotoxicity of pentachlorophenol to a marine bivalve species and potential toxification mechanisms underpinning

The ubiquitous presence of pentachlorophenol (PCP) in ocean environments threatens marine organisms. However, its effects on immunity of marine invertebrates at environmentally realistic levels are still largely unknown. In this study, the immunotoxicity of PCP to a representative bivalve species was evaluated. In addition, its impacts on metabolism, energy supply, detoxification, and oxidative stress status were also analysed by physiological examination as well as comparative transcriptomic and metabolomic analyses to reveal potential mechanisms underpinning. Results illustrated that the immunity of blood clams was evidently hampered upon PCP exposure. Additionally, significant alterations in energy metabolism were detected in PCP-exposed clams. Meanwhile, the expressions of key detoxification genes and the in vivo contents (or activity) of key detoxification enzymes were markedly altered. Exposure to PCP also triggered significant elevations in intracellular ROS and MDA whereas evident suppression of haemocyte viability. The abovementioned findings were further supported by transcriptomic and metabolomic analyses. Our results suggest that PCP may hamper the immunity of the blood clam by (i) constraining the cellular energy supply through disrupting metabolism; and (ii) damaging haemocytes through inducing oxidative stress. Considering the high similarity of immunity among species, many marine invertebrates may be threatened by PCP, which deserves more attention.

Hepatic transcriptomic and histopathological responses of common carp, Cyprinus carpio, to copper and microplastic exposure

The combined effects of copper and polyvinyl chloride (PVC) microparticles were investigated on the metal accumulation, histopathological biomarkers, and targeted transcriptomics in Cyprinus carpio liver. The fish were exposed to 0.25 mg/L copper and/or 0.5 mg/L PVC microparticles over a 14-d period. The results showed that hepatic copper accumulation is facilitated by the PVC microparticles presence in water. All treatments induced significant hepatic stress and inflammation; however, the transcriptional responses involving in detoxification pathways and apoptotic mechanisms were mixed and often down-regulated in the fish exposed to copper and/or PVC microparticles. Exposure to copper and/or PVC microparticles induced hypermeia, leukocyte infiltration and increase in melanomacrophage centers number and area. Generally, the severity of the lesions was in the following order: PVC microparticles < copper < copper+ PVC microparticles. In conclusion, PVC MPs act as a copper vector, facilitating accumulation of copper in the fish liver and increasing the tissue damage.

Immunotoxicities of microplastics and sertraline, alone and in combination, to a bivalve species: size-dependent interaction and potential toxication mechanism

Although coexposure to pharmaceuticals and microplastics (MPs) may frequently occur, the synergistic impact of MPs and antidepressants on marine species still remains poorly understood. In this study, the immunotoxicities of polystyrene MPs (diameters 500 nm and 30 μm) and sertraline (Ser), alone and in combination, were investigated in a bivalve mollusk Tegillarca granosa. Results showed that both MPs and Ser significantly suppressed the immune responses of T. granosa. In addition, though the toxic effect of Ser was not affected by microscale MPs, an evident synergistic immuno-toxic effect was observed between Ser and nanoscale MPs, which indicates a size-dependent interaction between the two. To further ascertain the underlying toxication mechanisms, the intracellular content of reactive oxygen species, apoptosis status, ATP content, pyruvate kinase activity, plasma cortisol level, and in vivo concentrations of neurotransmitters and cytochrome P450 1A1 were analysed. A transcriptomic analysis was also performed to reveal global molecular alterations following Ser and/or MPs exposure. The obtained results indicated that the presence of nanoscale MPs may enhance the immunotoxicity of Ser by (i) inducing apoptosis of haemocytes and, hence, reducing the THC; (ii) constraining the energy availability for phagocytosis; and (iii) hampering the detoxification of Ser.

Toxicological assessment and underlying mechanisms of tetrabromobisphenol A exposure on the soil nematode Caenorhabditis elegans

The widespread use of tetrabromobisphenol A (TBBPA) in industries has resulted in its frequent detection in environmental matrices, and the mechanisms of its associated hazards need further investigation. In this study, the nematode Caenorhabditis elegans (C. elegans) was exposed to environmentally relevant concentrations of TBBPA (0, 0.1, 1, 10, 100, 200 μg/L) to determine its effects. At TBBPA concentrations above 1 μg/L, the number of head thrashes, as the most sensitive physiological indicator, decreased significantly. Using the Illumina HiSeq™ 2000 sequencer, differentially expressed genes (DEGs) were determined, and 52 were down regulated and 105 were up regulated in the 200 μg/L TBBPA treatment group versus the control group. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway database analysis demonstrated that dorso-ventral axis formation is related to neurotoxicity; metabolism of xenobiotics by Cytochrome P450 (CYP450) and glutathione-S-transferase (GST) was found to be the vital metabolic mechanisms and were confirmed by quantitative real-time polymerase chain reaction (qRT-PCR). GST was ascribed to the augmentation because mutations in cyp-13A7 were constrained under TBBPA exposure. Additionally, oxidative stress indicators accumulated in a dose-dependent relationship. These results will help understand the molecular basis for TBBPA-induced toxicity in C. elegans and open novel avenues for facilitating the exploration of more efficient strategies against TBBPA toxicity.

Transcriptomic responses of the clam Meretrix meretrix to the organophosphorus pesticide (dimethoate)

Organophosphorus pesticides (OPs) play a certain role in promoting the development of agriculture and forestry, but they may cause potential harm to aquatic life when entering rivers and polluting water sources. Previous researches have shown that OPs participate in the regulation mechanism of aquatic organisms. Here, our aim is to determine the underlying mechanisms of one OP (dimethoate) at the transcriptional level using the clam Meretrix meretrix. 4119 DEGs were obtained from high-throughput RNA sequencing data. Then, expression profiles of some genes were verified by qPCR, which showed a positive correlation with the RNA sequencing results. 14,481 simple sequence repeats were also identified and could be further used as molecular markers. In addition, some oxidative, immune, and stress-related genes were further discussed and could also be used as biomarkers to indicate the biological response of dimethoate. This study will help to better understand the clam's response mechanism to dimethoate stress.

Biochemical and molecular biomarkers in integument biopsies of free-ranging coastal bottlenose dolphins from southern Brazil

Adverse effects of exposure to persistent organic pollutants (POPs) threaten the maintenance of odontocete populations. In southern Brazil, coastal bottlenose dolphins from the Laguna Estuarine System (LES) and Patos Lagoon Estuary (PLE) were sampled using remote biopsies during the winter and summer months. Levels of bioaccumulated POPs were measured in the blubber. The activities of glutathione S-transferase (GST), glutathione reductase (GR), glutathione peroxidase (GPx), and superoxide dismutase (SOD) were also quantified, as were the mRNA transcript levels of aryl hydrocarbon receptor (AhR), AhR nuclear translocator (ARNT), cytochrome P450 1A1-like (CYP1A1), metallothionein 2A (MT2A), GST-π, GPx-4, GR, interleukin 1 alpha (IL-1α), and major histocompatibility complex II (MHCII) in the skin. In general, levels of POPs were similar among sites, sexes, ages and seasons. For most animals, total polychlorinated biphenyl (ΣPCBs) levels were above the threshold level have physiological effects and pose risks to cetaceans. The best-fitting generalized linear models (GLMs) found significant associations between GR, IL-1α and GPx-4 transcript levels, SOD and GST activities, and total polybrominated diphenyl ether (ΣPBDEs) and pesticide levels. GLMs and Kruskal-Wallis analyses also indicated that there were higher transcript levels for most genes and lower GST activity in the winter. These results reinforce the need to consider the influence of environmental traits on biomarker values in wildlife assessments.

Lifetime extension of humpback whale skin fibroblasts and their response to lipopolysaccharide (LPS) and a mixture of polychlorinated biphenyls (Aroclor)

Marine mammals, such as whales, have a high proportion of body fat and so are susceptible to the accumulation, and associated detrimental health effects, of lipophilic environmental contaminants. Recently, we developed a wild-type cell line from humpback whale fibroblasts (HuWa). Extensive molecular assessments with mammalian wild-type cells are typically constrained by a finite life span, with cells eventually becoming senescent. Thus, the present work explored the possibility of preventing senescence in the HuWa cell line by transfection with plasmids encoding the simian virus large T antigen (SV40T) or telomerase reverse transcriptase (TERT). No stable expression was achieved upon SV40 transfection. Transfection with TERT, on the other hand, activated the expression of telomerase in HuWa cells. At the time of manuscript preparation, the transfected HuWa cells (HuWa_TERT) have been stable for at least 59 passages post-transfection. HuWa_TERT proliferate rapidly and maintain initial cell characteristics, such as morphology and chromosomal stability. The response of HuWa_TERT cells to an immune stimulant (lipopolysaccharide (LPS)) and an immunotoxicant (Aroclor1254) was assessed by measurement of intracellular levels of the pro-inflammatory cytokines interleukin (IL)-6, IL-1β and tumour necrosis factor (TNF)-α. HuWa_TERT cells constitutively express IL-6, IL-1β and TNFα. Exposure to neither LPS nor Aroclor1254 had an effect on the levels of these cytokines. Overall, this work supports the diverse applicability of HuWa cell lines in that they display reliable long-term preservation, susceptibility to exogenous gene transfer and enable the study of humpback whale-specific cellular response mechanisms.

Electron Spin Resonance (ESR) for the study of Reactive Oxygen Species (ROS) on the isolated frog skin (Pelophylax bergeri): A non-invasive method for environmental monitoring

BACKGROUND

Reactive oxygen species (ROS) in biological tissues of elected biosentinels represent an optimal biomarker for eco-monitoring of polluted areas. Electron spin resonance (ESR) is the most definitive method for detecting, quantifying and possibly identifying radicals in complex systems.

OBJECTIVE

A non-invasive method for monitoring polluted areas by the quantitative determination of ROS in frog skin biopsy is presented.

METHODS

We assessed by ESR spectroscopy the ROS level in adult male of Pelophylax bergeri, specie not a risk of extinction, collected from the polluted Sarno River (SA, Italy) basin. The spin-trap ESR method was validated by immunohistochemical analysis of the well-assessed pollution biomarkers cytochrome P450 aromatase 1A (CYP1A) and glutathione S-transferase (GST), and by determining the poly(ADPribose) polymerase (PARP) and GST enzymatic activity.

RESULTS

ROS concentration in skin samples from frogs collected in the polluted area is significantly higher than that determined for the unpolluted reference area. Immunohistochemical analysis of CYP1A and GST supported the reliability of our approach, even in the absence of evident morphological and ultrastructural differences. PARP activity assay, connected to possible oxidative DNA damage, and the detoxification index by GST enzymatic assay give statistically significant evidence that higher levels of ROS are associated to alterations of the different biomarkers.

CONCLUSIONS

ROS concentration, measured by ESR on isolated frog skin, through the presented non-lethal method, is a reliable biomarker for toxicity screening and represents a useful basic datum for future modelling studies on environmental monitoring and biodiversity loss prevention.

Halogen-free organophosphorus flame retardants caused oxidative stress and multixenobiotic resistance in Asian freshwater clams (Corbicula fluminea)

Halogen-free organophosphorus flame retardants are widespread in aquatic environments. Although it has been documented that they affect the behavior and reproduction of aquatic species, researches investigating cellular detoxification and the defense system in bivalves are scarce. In this study, adult Asian clams (C. fluminea) were exposed to tris (2-butoxyethyl) phosphate (TBEP) and tributyl phosphate (TBP) at 20, 200, and 2000 μg/L for 28 d. The results showed no noticeable difference in siphoning behavior. However, the siphoning behavior displayed a trend toward a slight decrease in the treatment groups. GR activity was markedly reduced compared with the control groups, whereas the levels of cyp4 significantly increased following the 2000 μg/L TBP treatments (p < 0.05). Moreover, the levels of gsts1 and gstm1 significantly decreased following all TBEP treatments and were significantly inhibited by 20 μg/L TBP (p < 0.05). The adverse effects on antioxidant enzymes suggested that C. fluminea mainly relies on the antioxidant system to reduce damage without an increase in MDA levels following exposure to a low concentration. Moreover, mRNA expression levels of heat shock proteins (hsp 22, 40, 60, 70, and 90) were significantly down-regulated with TBEP and TBP treatments lower than 200 μg/L (p < 0.05), whereas significant up-regulations were observed for hsp 22 and hsp 70 in response to 2000 μg/L TBP treatment (p < 0.05). Up-regulation of ATP-binding cassette (ABC) transporter genes (abcb1 and abcc1) showed that TBEP and TBP could activate the multixenobiotic resistance (MXR) system to discharge xenobiotics in C. fluminea, which kept its shell closed at high concentrations to prevent xenobiotic entry. Our results provide a new insight into the different mechanisms of cellular detoxification and the MXR system of C. fluminea in response to low and high concentrations of TBEP and TBP.

Isotopic Evidence of a Wide Spectrum of Feeding Strategies in Southern Hemisphere Humpback Whale Baleen Records

Our current understanding of Southern hemisphere humpback whale (Megaptera novaeangliae) ecology assumes high-fidelity feeding on Antarctic krill in Antarctic waters during summer, followed by fasting during their annual migration to and from equatorial breeding grounds. An increase in the number of reported departures from this feeding/fasting model suggests that the current model may be oversimplified or, alternatively, undergoing contemporary change. Information about the feeding and fasting cycles of the two Australian breeding populations of humpback whales were obtained through stable isotope analysis of baleen plates from stranded adult individuals. Comparison of isotope profiles showed that individuals from the West Australian breeding population strongly adhered to the classical feeding model. By contrast, East Australian population individuals demonstrated greater heterogeneity in their feeding. On a spectrum from exclusive Antarctic feeding to exclusive feeding in temperate waters, three different strategies were assigned and discussed: classical feeders, supplemental feeders, and temperate zone feeders. Diversity in the inter-annual feeding strategies of humpback whales demonstrates the feeding plasticity of the species, but could also be indicative of changing dynamics within the Antarctic sea-ice ecosystem. This study presents the first investigation of trophodynamics in Southern hemisphere humpback whales derived from baleen plates, and further provides the first estimates of baleen plate elongation rates in the species.

Opposing Lethal Wildlife Research When Nonlethal Methods Exist: Scientific Whaling as a Case Study

As our understanding of sentience in certain wildlife species grows, and technological advancements promote nonlethal data collection, we believe that we ought to adjust our field methods to incorporate a regime of best practice that prioritizes nonlethal methodologies over inhumane methods of lethal sampling. In addition, progress already made toward nonlethal methodologies in wildlife research needs to be promoted widely. In this paper, we examine whether lethal methods of whale research, using Japanese lethal scientific whaling as a case study, are ethical when the scientific information can be gained from nonlethal methods, and humane methods of killing are not available. As a part of a simple ethical decision-making model, we explore if a requirement for “refinement” of scientific technique, promoted extensively for laboratory-based animal experimentation, has direct applicability to scientific research involving free-living wildlife. We argue that refinement is an appropriate ethical principle in all cases where scientific research involves a choice between nonlethal sampling and the deliberate killing of free-living wildlife for scientific purposes. We conclude that the welfare of individual animals and the conservation of free-living wildlife populations are both worthy of moral consideration and need not be incompatible in humane wildlife research and management.

Isotopic Evidence of a Wide Spectrum of Feeding Strategies in Southern Hemisphere Humpback Whale Baleen Records

Our current understanding of Southern hemisphere humpback whale (Megaptera novaeangliae) ecology assumes high-fidelity feeding on Antarctic krill in Antarctic waters during summer, followed by fasting during their annual migration to and from equatorial breeding grounds. An increase in the number of reported departures from this feeding/fasting model suggests that the current model may be oversimplified or, alternatively, undergoing contemporary change. Information about the feeding and fasting cycles of the two Australian breeding populations of humpback whales were obtained through stable isotope analysis of baleen plates from stranded adult individuals. Comparison of isotope profiles showed that individuals from the West Australian breeding population strongly adhered to the classical feeding model. By contrast, East Australian population individuals demonstrated greater heterogeneity in their feeding. On a spectrum from exclusive Antarctic feeding to exclusive feeding in temperate waters, three different strategies were assigned and discussed: classical feeders, supplemental feeders, and temperate zone feeders. Diversity in the inter-annual feeding strategies of humpback whales demonstrates the feeding plasticity of the species, but could also be indicative of changing dynamics within the Antarctic sea-ice ecosystem. This study presents the first investigation of trophodynamics in Southern hemisphere humpback whales derived from baleen plates, and further provides the first estimates of baleen plate elongation rates in the species.

Establishment of the first humpback whale fibroblast cell lines and their application in chemical risk assessment

This paper reports the first successful derivation and characterization of humpback whale fibroblast cell lines. Primary fibroblasts were isolated from the dermal connective tissue of skin biopsies, cultured at 37 °C and 5% CO2 in the standard mammalian medium DMEM/F12 supplemented with 10% fetal bovine serum (FBS). Of nine initial biopsies, two cell lines were established from two different animals and designated HuWa1 and HuWa2. The cells have a stable karyotype with 2n=44, which has commonly been observed in other baleen whale species. Cells were verified as being fibroblasts based on their spindle-shaped morphology, adherence to plastic and positive immunoreaction to vimentin. Population doubling time was determined to be ∼41 h and cells were successfully cryopreserved and thawed. To date, HuWa1 cells have been propagated 30 times. Cells proliferate at the tested temperatures, 30, 33.5 and 37 °C, but show the highest rate of proliferation at 37 °C. Short-term exposure to para,para'-dichlorodiphenyldichloroethylene (p,p'-DDE), a priority compound accumulating in southern hemisphere humpback whales, resulted in a concentration-dependent loss of cell viability. The effective concentration which caused a 50% reduction in HuWa1 cell viability (EC50 value) was approximately six times greater than the EC50 value for the same chemical measured with human dermal fibroblasts. HuWa1 exposed to a natural, p,p'-DDE-containing, chemical mixture extracted from whale blubber showed distinctively higher sensitivity than to p,p'-DDE alone. Thus, we provide the first cytotoxicological data for humpback whales and with establishment of the HuWa cell lines, a unique in vitro model for the study of the whales' sensitivity and cellular response to chemicals and other environmental stressors.

Organochlorine pesticides and PCBs in Southern Right Whales (Eubalaena australis) breeding at Península Valdés, Argentina

Organochlorine pesticides (OCPs) and polychlorinated biphenyls (PCBs) were assessed in blubber from 35 dead Southern Right Whales (SRW - Eubalaena australis) stranded at Península Valdés, Argentina. The life cycle includes a feeding period in high productivity areas of the South West Atlantic and a reproductive period in coastal template waters of Argentina. Organochlorine pesticides showed higher concentrations (22.6±13.8 ng·g(-1)ww) than PCBs (7.5±10 ng·g(-1)ww). Among pesticides, HCHs, DDTs, endosulfans, dieldrin, chlordans, heptachlor epoxide, and trans-nonachlor were detected. p,p'-DDE and p,p'-DDT were present in 69% and 26% of samples, respectively. p,p'-DDT/p,p'-DDE ratio showed low values (<0.33) as a result of aged DDT inputs. However, the occurrence of only p,p'-DDT in some samples suggests a recent pesticide input. α-HCH/γ-HCH ratio (<DL-0.37) indicated no recent contribution of technical HCH mixture and/or current use of lindane. Dieldrin was present in 77% of the samples and endosulfan was detected in all samples with predominance of α- (75%) over β-endosulfan (19%) and scarce contribution of endosulfan sulphate (7%), suggesting a recent input of this insecticide to the environment in the SRW foraging area. A predominance of pentachlorobiphenyls was observed. In 21 samples at least one PCB indicator was found and PCB #118, highly toxic, contributed in 5% to total PCBs. Although all these organochlorine compounds are forbidden they were bioaccumulated in the blubber of SRW with a predominance of endosulfans, the more recently used pesticide. The absence of data on chemical pollutants in stranded dead whales is highlighted as a priority for research. This is the first study on levels, compositional patterns, and organochlorine sources in SRW. Moreover, more research including milk, and other tissues/organs is recommended considered that in the studied specimens, mostly calves, pollutants are likely transferred from the mother during pregnancy and nursing.