Oxidative stress and immunologic responses following a dietary exposure to PAHs in Mya arenaria

Organic UV Filters Induce Toll-like-Receptors and Related Signaling Pathways in Peripheral Blood Mononuclear Cells of Juvenile Loggerhead Sea Turtles (Caretta caretta)

Simple Summary

Emerging environmental contaminants, such as sunscreen agents, have been broadly identified in marine ecosystems. Thus, the present work aims to investigate whether organic UV filters cause immunotoxic effects in juvenile loggerhead sea turtles (Caretta caretta). We found that loggerhead sea turtles showing high circulating levels of organic UV filters manifested increased expression of genes involved in inflammatory responses, probably due to contaminant-induced oxidative damage.

Abstract

Recent evidence suggests that exposure to organic ultraviolet filters (UV filters) is associated with dysregulated neuroendocrine-immune homeostasis. Marine species are likely to be among the most vulnerable to UV filters due to widespread diffusion of these chemicals in the aquatic environment. In the present study, the effects of UV filter bioaccumulation on toll-like-receptors (TLRs) and related signaling pathways were investigated in peripheral blood mononuclear cells (PBMCs) of juvenile loggerhead sea turtles (Caretta caretta). We found that the expression of both TLR1 and TLR2 was significantly increased in UV-filter exposed turtles compared to control animals. Similarly, the signaling pathway downstream of activated TLRs (i.e., Ras-related C3 botulinum toxin substrate 1 (RAC1), Phosphoinositide 3-kinase (PI3K), serine/threonine-protein kinase (AKT3), and nuclear factor κB (NF-κB)) was significantly up-regulated, leading to an enhanced transcription of pro-inflammatory cytokines. In addition, we demonstrated that high levels of plasma UV filters increased lipid peroxidation in sea turtles’ PBMCs. Our results indicated that UV filters affected the inflammatory responses of PBMCs via modulation of the TLR/NF-κB signaling pathway and provided a new insight into the link between exposure to sunscreen agents and sea turtle health.

Can Microplastics Influence the Accumulation of Pb in Tissues of Blue Crab?

The study of microplastics (MPs) and associated pollutants is essential for a better understanding of some of the factors that threaten marine ecosystems. The main objective of this study was thus to assess Pb distribution and accumulation in the tissues of blue crabs (Callinectes sapidus) exposed to MPs. Blue crabs were collected from the mouth of the river Segura (Guardamar, Spain) and fed on mussels from two Mediterranean areas with different levels of Pb contamination: Portmán Bay and San Pedro del Pinatar (Murcia, Spain). In addition, a batch of each group were exposed to MPs. After seven days of exposure, the crabs were euthanised, and tissues and faeces were analysed. The hepatopancreas was found to be the best tissue for measuring Pb concentrations after feeding; muscle tissue did not provide information on environmental quality. The meat (muscle) consumption of blue crabs from zones with high Pb content does not seem to constitute a risk for consumers, although the risk is not totally negated if all soft tissues are ingested. The presence of MPs in the water does not seem to increase the accumulation of Pb in these tissues of C. sapidus.

How leachates from wasted cigarette butts influence aquatic life? A case study on freshwater mussel Anodontites trapesiali

There are several reports on the damage smoking causes to human health available in the literature, but little is known about the environmental and biological consequences from inappropriate cigarette butt (CB) disposal in urban and natural environments. The immunotoxic, morphotoxic and mutagenic potential of leachates from cigarette butts (LCB) diluted at environmentally relevant rates (LCB1x: 1.375%; LCB10x: 13.75%) was evaluated in adult representatives of the bivalve species Anodontites trapesialis, which was adopted as model organism. Type II hyalinocytes and granulocytes (phagocytic cells) frequency increased in the hemolymph of subjects exposed to the pollutant for 14 days. Based on this outcome, LCB chemical constituents did not induce immunotoxic effects. The treatments also did not seem to have any impact on the subjects' hemocitary morphometry parameters: diameter, area, perimeter, circularity and nucleus - cytoplasm ratio. However, subjects in groups LCB1x and LCB10x recorded a larger number of hyalinocytes with some nuclear abnormality such as micronucleus, blebbed nucleus, asymmetric constriction nucleus, and nuclear multilobulation and binucleation. The association between these abnormalities and the treatments was confirmed by the Cr, Ni, Pb, Zn, Mn and Na bioaccumulation in tissue samples of the bivalve models exposed to LCB. To the best of our knowledge, this is the first report on LCB mutagenicity in representatives of a freshwater bivalve group. Given the chemical complexity of the addressed pollutants, it is imperative to develop further investigations about the topic.

Three simple biomarkers useful in conducting water quality assessments with bivalve mollusks

While biomarkers are undeniably key tools in aquatic ecotoxicology to measure adverse effects linked to contamination events, their application is often inhibited by monetary constraints negating the possibility of having access to dedicated equipment, special wares, and/or expensive reagents. To offset this bottleneck, we propose three simple physiological biomarkers, quantifiable in bivalves, that are free of cost considerations and that can provide basic knowledge on animal health and water quality. Indeed, condition index (CI), growth index (GI), and SOS response (air-time survival) comprise measurements straightforward enough to perform by any laboratory or science body on the planet. Long-term monitoring or screening studies can be carried out with these biomarkers and they are able to provide robust information notably after exposure of bivalves to either singular or multiple agents of contamination. By highlighting examples of data generated in aquatic studies conducted in Eastern Canada under both laboratory and field situations with different species of marine and freshwater mollusks, we establish the suitability of these biomarkers for assessing environmental contamination. Their relationships with other biomarkers are also shown which further corroborate their value as reliable indicators of ecosystem health.

Combination of polycyclic aromatic hydrocarbons and temperature exposure: In vitro effects on immune response of European clam (Ruditapes decussatus)

Marine organisms are subjected to various biotic and abiotic factors such as changes of temperature and pollutants [e.g. polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and heavy metals, which may affect their defense mechanisms. In this context, the aim was to evaluate the combined effects of temperature (20 and 30 °C) and PAHs (fluorene, phenanthrene and pyrene) at two concentrations (10^-5 and 10^-3 mg mL^-1) on the immune responses of the European clam Ruditapes decussatus were after 24 h of in vitro exposure. Total haemocyte count, cell viability, phenoloxidase, lysozyme, alkaline phosphatase, esterase, antibacterial and agglutinating activities were measured. Exposure to high temperatures resulted in lower phosphatase alkaline activity and higher haemocyte viability and antibacterial and haemagglutinating activities, compared with the values recorded for clams maintained at low temperature. Only pyrene induced a significant decrease in haemocyte lysozyme (at 20 and 30 °C) and esterase (at 30 °C) activities. The total haemocyte count was increased by phenanthrene and pyrene at 20 °C and at 30 °C, respectively. Alkaline phosphatase activity increased when haemocytes were exposed to pyrene at 30 °C but decreased in the presence of fluorene at 20 °C. Furthermore, haemocyte viability was low in the presence of pyrene and fluorene at 20 °C and 30 °C, respectively, but was unaffected by phenanthrene. Antibacterial activity was significantly increased and no-significantly affected by the presence of pyrene and fluorene at 20 °C and 30 °C, respectively. The present study demonstrates the strong effect of PAHs and high temperature on haemocyte viability and other important immune functions, including phosphatase alkaline and antibacterial activities. Furthermore, changes in the immune parameters of European clam resulting from high temperatures may modulate the effects of PAHs and vice versa.

Dechlorane Plus induces oxidative stress and decreases cyclooxygenase activity in the blue mussel

Dechlorane Plus (DP) is a chlorinated flame retardant used mainly in electrical wire and cable coating, computer connectors, and plastic roofing materials. Concentrations of DP (syn and anti isomers) are increasingly being reported in aquatic ecosystems worldwide. However, there is exceedingly little information on the exposure-related toxicity of DP in aquatic organisms, especially in bivalves. The objective of this study was to investigate the in vivo and in vitro effects of DP exposure on histopathology, lipid peroxidation (LPO) levels, cyclooxygenase (COX) activity, phagocytosis capacity and efficiency, and DNA strand breakage in the blue mussel (Mytilus edulis) following a 29days exposure (0.001, 0.01, 0.1 and 1.0μg DP/L). Blue mussels accumulated DP in muscle and digestive gland in a dose-dependent manner. LPO levels in gills were found to increase by 82% and 67% at the 0.01 and 1.0μg DP/L doses, respectively, while COX activity in gills decreased by 44% at the 1μg/L dose. No histopathological lesion was found in gonads following DP exposure. Moreover, no change in hemocyte DNA strand breakage, phagocytosis rate, and viability was observed following DP exposure. Present study showed that toxicity of DP may occur primarily via oxidative stress in the blue mussel and potentially other bivalves, and that gills represent the most responsive tissue to this exposure.

Effects of pyrene exposure on immune response and oxidative stress in the pearl oyster, Pinctada martensii

Pyrene is a polycyclic aromatic hydrocarbon (PAH) commonly observed in aquatic ecosystems, which originates primarily from the incomplete combustion of fossil fuels and the use of petroleum compounds. Pyrene can cause the immune disturbance and oxidative stress, result in immunotoxicity, DNA damage, reduce reproduction significantly, and induce behavioral changes. Marine bivalves are commonly used as bioindicators for marine pollution, and hemolymph is a metabolite transfer medium for PAH pollutant. However, the vital immune indicator responses of pearl oyster Pinctada martensii hemolymph exposed to pyrene is still unclear. Thus, the immunotoxic responses of pyrene on the hemolymph of the Pinctada martensii were investigated in this study. After exposure to pyrene for 7 days, the total number of hemocytes (THC), cell membrane stability (CMS), phagocytic activity (PA) and total glutathione (GSH_T) all decreased significantly. Pyrene also caused a significant increase in lipid peroxidation (LPO). Median effective concentrations (EC₅₀) of pyrene on THC (4.5 μg L^-1) and LPO (5.2 μg L^-1) were lower than those for CMS (13.8 μg L^-1), PA (12.1 μg L^-1) and GSH_T (7.2 μg L^-1), which indicates that THC and LPO were more sensitive. Additionally, a clear dose-effect relationship indicated that pyrene stimulated a marked immune response, as well as oxidative stress in P. martensii, which demonstrates the subtle effects of pyrene exposure on marine invertebrates and the potential associated risk.

Never deem lightly the "less harmful" low-molecular-weight PAH, NPAH, and OPAH - Disturbance of the immune response at real environmental levels

The upcoming energy structure optimization and the implementation of strict emissions control will effectively alleviated the pollution of high-molecular-weight (HMW) polycyclic aromatic hydrocarbons (PAHs) in the atmosphere. Compared to HMW PAHs, the immune response to low-molecular-weight (LMW) PAHs is recognized as "less harmful", despite the high proportions of these substances. The present study intends to investigate the effects of several of the most abundant LMW PAHs on macrophages RAW264.7 at environmentally relevant doses. The data assembled herein showed that Fluoranthene (Fluo, PAH) formed a π-π interaction with the Phe12 residue of AhR while inhibiting the transcription of CYP1A1 and CYP1B1, and ultimately induced the inflammatory cytokines in RAW264.7. The 1-Nitropyrene (1-Nitro, NPAH) formed both a π-π interaction and a hydrogen bond with AhR, stimulated CYP1A1transcription, while suppressed the cytokine levels. Additionally, the inflammation potency caused by TPAHs was highly correlated with the cytotoxic potency rather than the oxidative stress potency. When stimulated by LPS, the transcription of IL-6 was inhibited by Fluo, and 1-Nitro suppressed both IL-6 and TNFα transcription. Furthermore, only 1-Nitro gave a significant inhibition on phagocytosis. The effects of 9-Fluorenone (9-Fluo, OPAH) on macrophages remained insignificant throughout the study since the low affinity for AhR, which resulted in low cytotoxicity. Collectively, this study suggested that LMW PAHs tended to cause mild inflammation when they bind without activating AhR. During infection, AhR ligands caused immunosuppression and this potency for TPAHs may be higher in AhR activator than that in AhR inactivator.

The impact of endocrine-disrupting chemicals on oxidative stress and innate immune response in zebrafish embryos

Bisphenol A (BPA) and nonylphenol (NP) are well known endocrine-disrupting chemicals (EDCs) ubiquitous in the aquatic environment and are an ecotoxicological risk for the health of aquatic organisms. Limited attention has been given to the immunotoxicity of these chemicals. The present study revealed a concentration-dependent increase of reactive oxygen species content and an induced expression of redox-sensitive transcription factors in zebrafish embryos after exposure to various concentrations of BPA, NP, and BPA/NP mixture for 4 h to 168 h postfertilization. Transcription of genes related to the immune response, including IFNγ, IL1β, IL10, Mx, TNFα, CC-chemokine, and CXCL-clc, were significantly up-regulated on exposure to EDCs. A significant induction of concentrations of proinflammatory mediator, nitric oxide, accompanied by an increase in the activity of nitric oxide synthase (NOS) and an upregulation of inducible NOS gene expression, was detected in zebrafish embryos on exposures to EDCs. To elucidate the potential mechanisms by which BPA and NP activate the innate immune response, expression profiles of genes related to the Toll-like receptors (TLRs) signaling pathway were examined. Expressions of TLR3, TRIF, MyD88, SARM, IRAK4, and TRAF6 were altered on exposure to EDCs. The authors' results demonstrate that exposure to BPA and NP significantly affects the expression of genes related to immune response in zebrafish embryos following oxidative stress.

Cytotoxicity of water-soluble mPEG-SH-coated silver nanoparticles in HL-7702 cells

Silver nanoparticles (AgNPs) are being used widely and increasingly in various products and medical supplies due to their antibacterial activity. However, little is known about the impacts of the AgNPs. Herein, The primary purpose of this study was to investigate the cytotoxic effect of AgNPs in the human liver cell line (HL-7702). The water-soluble α-Methoxy-poly (ethylene glycol)-ω-mercapto (mPEG-SH)-coated AgNPs (40 nm) were synthesized, which showed superior stabilization and uniform dispersion in culture medium. The effect of mPEG-SH-coated silver nanoparticles on cell viability, leakage of lactate dehydrogenase (LDH), oxidative stress, mitochondrial membrane potential (MMP), and cell cycle was evaluated after the cells were treated with nanoparticles. The results showed that the coated AgNPs could be taken up by cells, decreased cell viability in dose- and time-dependent manners at dosage levels between 6.25 and 100.00 μg/mL, caused membrane damage (LDH leakage), and decreased the activities of superoxide dismutase and glutathione peroxides. The level of malondialdehyde, an end product of lipid peroxidation, was also increased in AgNPs-exposed cells. Moreover, flow cytometric analysis showed that AgNP exposure decrease MMP and cause G₂/M phase arrest. Thus, our data suggest that mPEG-SH-coated AgNPs have the potential toxicity that is associated with oxidative stress, apoptosis, and DNA damage.

Ecotoxicological evaluation of tributyltin toxicity to the equilateral venus clam, Gomphina veneriformis (Bivalvia: Veneridae)

Tributyltin (TBT) is the most common pesticide in marine and freshwater environments. To evaluate the potential ecological risk posed by TBT, we measured biological responses such as growth rate, gonad index, sex ratio, the percentage of intersex gonads, filtration rate, and gill abnormalities in the equilateral venus clam (Gomphina veneriformis). Additionally, the biochemical and molecular responses were evaluated in G. veneriformis exposed to various concentrations of TBT. The growth of G. veneriformis was significantly delayed in a dose-dependent manner after exposure to all tested TBT concentrations. After TBT was administered to G. veneriformis, the gonad index decreased and the sex balance was altered. The percentage of intersex gonads also increased significantly in treated females, whereas no intersex gonads were detected in the solvent control group. Additionally, intersex gonads were detected in male G. veneriformis specimens exposed to relatively high TBT concentrations (20 μg L⁻¹). The filtration rate was also reduced in a dose-dependent manner in TBT-exposed G. veneriformis. We also noted abnormal gill morphology in TBT-exposed G. veneriformis. Furthermore, increases in antioxidant enzyme activities were observed in TBT-exposed G. veneriformis clams, regardless of dosage. Vitellogenin gene expression also increased significantly in a dose-dependent manner in G. veneriformis exposed to TBT. These results provide valuable information regarding our understanding of the toxicology of TBT in G. veneriformis. Moreover, the responses of biological and molecular factors could be utilized as information for risk assessments and marine monitoring of TBT toxicity.

Validation of Arenicola marina in field toxicity bioassays using benthic cages: biomarkers as tools for assessing sediment quality

Sediment toxicity assessments using caged organisms present advantages over using laboratory and native community studies. The use of caged Arenicola marina in sediment toxicity assessments was evaluated. Lugworms were exposed in situ to sediments from coastal and port areas in Spain for seven days, and the activities of the biotransformation enzymes ethoxyresorufin O-deethylase, dibenzylfluorescein dealkylase and glutathione S-transferase, the activities of the antioxidant enzymes glutathione reductase and glutathione peroxidase and lipid peroxidation were then analyzed as biomarkers. Biomarker results and sediment physicochemical data were integrated. Cádiz Bay (SW Spain) sediments presented metal contamination that was not linked to a biochemical response. In LPGC Port (SW Spain), Pb contamination exhibited a moderate toxic potential, while PAHs, and presumably pharmaceuticals, provoked biochemical responses that efficiently prevented lipid peroxidation. In Santander Bay (N Spain), exposure to PAHs and, presumably, pharmaceuticals induced biomarker responses, but lipid peroxidation occurred nevertheless. These results indicated that caged A. marina were effective for the assessment of sediment quality and that the selected biomarkers were sufficiently sensitive to identify chemical exposure and toxicity.

Immunotoxicity and oxidative stress in the Arctic scallop Chlamys islandica: effects of acute oil exposure

With increasing oil exploration in Arctic regions, the risk of an accidental oil spill into the environment is inevitably elevated. As a result, concerns have been raised over the potential impact of oil exposure on Arctic organisms. This study assessed the effects of an acute oil exposure (mimicking an accidental spill) on the immune function and oxidative stress status of the Arctic scallop Chlamys islandica. Scallops were exposed to the water accommodated fraction of crude oil over 21 d (maximum SigmaPAH 163 microg l(-1)) and immune endpoints and oxidative stress parameters were measured. Mortalities were recorded during the exposure and reductions in immunocompetence were observed, with significant impairment of phagocytosis and cell membrane stability. Scallops were also subjected to oxidative stress, with a significant reduction in glutathione levels and induction of lipid peroxidation. After the acute oil exposure had subsided, no recovery of immune function was observed indicating potential for prolonged sublethal effects.