Gene cloning and expression analysis of AhR and CYP4 from Pinctada martensii after exposed to pyrene

Polycyclic aromatic hydrocarbons in commercial marine bivalves: Abundance, main impacts of single and combined exposure and potential impacts for human health

Polycyclic aromatic hydrocarbons (PAHs) are emerging pollutants with a broad distribution in marine environments. They can interact with other pollutants and be bioaccumulated by marine bivalves, which can be consumed by humans. This is the first review that focuses on the presence and effects of PAHs, single or combined with other pollutants, in commercial marine bivalves. Around the world, researchers have detected several PAHs in valuable marine bivalves and reported immunological, genotoxic, neurotoxic, physiological, reproductive, and biochemical effects in these species caused by exposure to PAHs, alone or combined with other pollutants, using efficient and accurate methods. Commercial marine bivalves contaminated with PAHs may pose a risk to marine food chains and environments and to human health. We recommend further research on the abundance and neurotoxic, physiological, reproductive and biochemical effects of PAHs, alone and with other pollutants, in commercial marine bivalves and more human health risk assessments.

Persistent organic pollutants (POPs) in marine crustaceans: Bioaccumulation, physiological and cellular responses

Persistent organic pollutants (POPs) are ubiquitous in marine ecosystems. These compounds can be accumulated in water, sediments and organisms, persist in time, and have toxic effects in human and wildlife. POPs can be uptaken and bioaccumulated by crustaceans, affecting different physiological processes, including energy metabolism, immunity, osmoregulation, excretion, growth, and reproduction. Nonetheless, animals have evolved sub-cellular mechanisms for detoxification and protection from chemical stress. POPs induce the activity of enzymes involved in xenobiotic metabolism and antioxidant systems, that in vertebrates are importantly regulated at gene expression (transcriptional) level. However, the activation and control of these enzyme systems upon the exposure to POPs have been scarcely studied in invertebrate species, including crustaceans. Herein, we summarize various aspects of the bioaccumulation of POPs in marine crustaceans and their physiological effects. We specially focus on the regulation of xenobiotics metabolism and antioxidant enzymes as key sub-cellular mechanisms for detoxification and protection from chemical stress.

Emerging studies on oil pollution biomonitoring: A systematic review

In the last decade, several methods were applied to monitor the impact of oil pollution on marine organisms. Recent studies showed an eminent need to standardize these methods to produce comparable results. Here we present the first thorough systematic review of the literature on oil pollution monitoring methods in the last decade. The literature search resulted on 390 selected original articles, categorized according to the analytical method employed. Except for Ecosystem-level analyses, most methods are used on short-term studies. The combination of Biomarker and Bioaccumulation analysis is the most frequently adopted strategy for oil pollution biomonitoring, followed by Omic analyses. This systematic review describes the principles of the most frequently used monitoring tools, presents their advantages, limitations, and main findings and, as such, could be used as a guideline for future researches on the field.

Microplastics boost the accumulation of tetrabromobisphenol A in a commercial clam and elevate corresponding food safety risks

Marine bivalve molluscs are one of the primary seafood for consumers. Inhabiting terrigenous pollutant-convergent coastal areas and feeding through seawater filtration, edible bivalves are subjected to waterborne emerging pollutants such as microplastics (MPs) and tetrabromobisphenol A (TBBPA). Nevertheless, the potential risks of consuming MP-TBBPA contaminated seafood are still largely unknown. With that, accumulation of TBBPA with and without the presence of MPs in a commercial bivalve species, blood clam (Tegillarca granosa), was determined in the present study. Meanwhile, corresponding target hazard quotients (THQs) as well as margins of exposure (MoEs) were estimated to evaluate the potential health risks for clam consumers. Furthermore, the impacts of pollutants accumulation on the detoxification process and energy supply were analysed. The data obtained demonstrated that MPs aggravate the accumulation of TBBPA in clams, leading to elevated potential food safety risks (indicated by higher THQ values and lower MoE values) for consumers. In addition, the in vivo contents of CYP1A1 and UDP-glucuronosyltransferase, the enzymatic activity of glutathione-S-transferase, and the expression levels of five detoxification-related genes were all dramatically suppressed by MP-TBBPA. Furthermore, clams exposed to MP-TBBPA had significantly lower adenosine triphosphate contents and lower pyruvate kinase and phosphofructokinase activities. These results indicated that the aggravation of TBBPA accumulation may be due to the hence disruption of detoxification process and limited energy available for detoxification.

Fine particulate matter and vasoactive 20-hydroxyeicosatetraenoic acid: Insights into the mechanisms of the prohypertensive effects of particulate air pollution

BACKGROUND

Emerging evidence suggests that biological intermediates play an important role in initiating fine particulate matter (PM_2.5)-associated prohypertensive pathways, but sensitive biomarkers for this pathway are lacking.

AIM

To explore whether short-term exposure to PM_2.5 is associated with the concentration of 20-hydroxyeicosatetraenoic acid (20-HETE), a potent vasoactive lipid relevant to the pathophysiology of hypertension.

METHODS

In this longitudinal panel study, we repeatedly (up to seven times) measured the blood concentrations of 20-HETE in 120 adults living in Beijing, China. Ambient exposure metrics included the concentrations of hourly PM_2.5 mass and daily PM_2.5 constituents, including three carbonaceous components, eight water-soluble ions, and 16 trace elements. Linear mixed-effects models were used to examine the associations between the change in the 20-HETE concentration and short-term exposure to ambient PM_2.5 metrics after adjustment for age, sex, body mass index, behavioral exposure, socioeconomic characteristics, and meteorological factors.

RESULTS

The interquartile range (IQR) increase in the 7-15-hour-lag exposure to PM_2.5 (80 μg/m³) was associated significantly with a 5.3% (95% confidence interval [CI], 0.1-10.7%) to 6.5% (95% CI, 1.7-11.6%) increase in the blood concentration of 20-HETE. The magnitude of the association differed by age, sex, prediabetic status, obesity, and hypertensive status, with a significantly greater increase in 20-HETE observed among those with fasting plasma glucose concentrations ≥ 6.1 mmol/L. In addition to the PM_2.5 mass, the 20-HETE concentration was associated consistently with IQR increases in the 1-day lag exposure to organic carbon (5.7%), black carbon (9.5%), nitrate (3.9%), chloride (2.9%), copper (5.5%), zinc (4.7%), barium (4.1%), and lead (6.2%). The organic carbon estimate was robust in the two-pollutant models. Furthermore, increased 20-HETE correlated with elevated blood pressure (BP), although no mediation of 20-HETE on PM_2.5-associated BP change was found.

CONCLUSIONS

The 20-HETE blood concentration increased significantly in response to short-term exposure to ambient PM_2.5, which may be partly responsible for the prohypertensive effects of PM_2.5.

A verification of correlation between chemical monitoring and multi-biomarker approach using clam Ruditapes philippinarum and scallop Chlamys farreri to assess the impact of pollution in Shandong coastal area of China

Biogeochemical monitoring coupled with multi-biomarker approach were performed for the assessment of marine environment, using clam Ruditapes philippinarum and scallop Chlamys farreri to indicate contamination status in sediments and seawater respectively. The bivalves were collected from three stations, Jiaozhou Bay, Rushan Bay and Laizhou Bay, of Shandong coastal area. A series of contaminants (PAHs and TBBPA) and biomarkers (AhR, EROD, GST, SOD, GPx, CAT, DNA damage) were measured. Multi-biomarker pollution index (MPI) and integrated biomarker response (IBR) were carried out to evaluate contamination status and both indexes showed that Rushan Bay was most polluted, where the pollution level of sediments reached "highly polluted" in August, followed by Jiaozhou Bay and Rushan Bay which reached "lightly polluted". The correlation of IBR values with contaminants' concentrations was verified through the Pearson correlation coefficient (p < 0.05), consolidating this scientific assessment method for marine environment.

Effect of Polycyclic Aromatic Hydrocarbons on Development of the Ascidian Ciona intestinalis Type A

Polycyclic aromatic hydrocarbons (PAHs) are pollutants that exert harmful effects on marine invertebrates; however, the molecular mechanism underlying PAH action remains unclear. We investigated the effect of PAHs on the ascidian Ciona intestinalis type A (Ciona robusta). First, the influence of PAHs on early Ciona development was evaluated. PAHs such as dibenzothiophene, fluorene, and phenanthrene resulted in formation of abnormal larvae. PAH treatment of swimming larva induced malformation in the form of tail regression. Additionally, we observed the Cionaaryl hydrocarbon receptor (Ci-AhR) mRNA expression in swimming larva, mid body axis rotation, and early juvenile stages. The time correlation between PAH action and AhR mRNA expression suggested that Ci-AhR could be associated with PAH metabolism. Lastly, we analyzed Ci-AhR mRNA localization in Ciona juveniles. Ci-AhR mRNA was localized in the digestive tract, dorsal tubercle, ganglion, and papillae of the branchial sac, suggesting that Ci-AhR is a candidate for an environmental pollutant sensor and performs a neural function. Our results provide basic knowledge on the biological function of Ci-AhR and PAH activity in marine invertebrates.

Molecular characterisation of cytochrome P450 enzymes in waterflea (Daphnia pulex) and their expression regulation by polystyrene nanoplastics

Cytochrome P450 (CYP) enzymes are one of the largest protein families, and they metabolise a wide range of lipophilic organic endogenous and exogenous compounds. Many cytochrome P450 genes have been cloned and characterised, and they are frequently used as biomarkers in environmental toxicology studies because of their sensitivity and inducibility. In the present study, the full-length cDNAs of DpCYP370B and DpCYP4 were cloned from Daphnia pulex for the first time. The sequence of DpCYP370B consisted of an ORF of 1515 bp that encoded a 504 amino acid polypeptide, while the sequence of DpCYP4 comprised an ORF of 1527 bp that encoded a 508 amino acid polypeptide. Homologous alignments revealed the presence of a conserved cysteine haeme-iron ligand signature, FxxGxxxCxG, located in the C-terminal portion. Both the proteins contained a sequence for a transmembrane region that was deduced to be located in the endoplasmic reticulum. Subsequently, the expression levels of DpCYP370B and DpCYP4, as well as those of CYP4AN1, CYP4C33, and CYP4C34, were investigated using quantitative real-time PCR after exposure to five polystyrene nanoplastic concentrations: 0 (control), 0.1, 0.5, 1, and 2 mg/L for 21 days. Except for DpCYP4, the highest mRNA expression was observed at 0.5 mg/L nanoplastics; next, the expression of three of the enzymes (DpCYP370B, CYP4AN1, CYP4C34,) decreased to that of the control level at 1 and 2 mg/L doses of nanoplastics. The expression of DpCYP4 did not significantly change compared with that of the control group. These results indicated that CYP genes might play an important role in protecting D. pulex against nanoplastic pollutants.

Gene expression and genotoxicity in Manila clam (Ruditapes philippinarum) modulated by sediment contamination and lagoon dynamics in the Po river delta

The lagoons of the Po River delta are potentially exposed to complex mixtures of contaminants, nevertheless, there is a substantial lack of information about the biological effects of these contaminants in the Po delta lagoons. These environments are highly dynamic and the interactions between chemical and environmental stressors could prevent the proper identification of biological effects and their causes. In this study, we aimed to disentangle such interactions focusing on Manila clams, previously exposed to six lagoons of the Po delta, adopting three complementary tools: a) the detailed description via modelling techniques of lagoon dynamics for salinity and water temperature; b) the response sensitivity of a number of target genes (ahr, cyp4, ρ-gst, σ-gst, hsp22, hsp70, hsp90, ikb, dbh, ach, cat, Mn-sod, Cu/Zn-sod, cyp-a, flp, grx, TrxP) investigated in clam digestive glands by Real Time PCR; and c) the relevance of DNA adducts determined in clams as markers of exposure to genotoxic chemicals. The lagoons showed specific dynamics, and two of them (Marinetta and Canarin) could induce osmotic stress. A group of genes (ahr, cyp4, Mn-sod, σ-gst, hsp-22, cyp-a, TrxP) seemed to be associated with overall lagoon characteristics as may be described by salinity and its variations. Lagoon modelling and a second group of genes (hsp70, hsp90, cat, ikb, ach, grx, Cu/Zn-sod) also suggested that moderate increases of river discharge may imply worse exposure conditions. Oxidative stress seemed to be associated with such events but it was slightly evident also under normal exposure conditions. DNA adduct formation was mainly associated with overwhelmed antioxidant defences (e.g. low Cu/Zn-sod) or seemingly with their lack of response in due time. In Po delta lagoons, Manila clam can be affected by chemical and environmental factors which can contribute to induce oxidative stress, DNA adduct formation and, ultimately, to affect clam condition and health.

An integrated metabolomic and proteomic study of toxic effects of Benzo[a]pyrene on gills of the pearl oyster Pinctada martensii

Benzo[a]pyrene (BaP) is one of the most important polycyclic aromatic hydrocarbons (PAHs), which are widely present in the marine environment. Because of its teratogenic, mutagenic, and carcinogenic effects on various organisms, the toxicity of BaP is of great concern. In this study, we focused on the toxic effects of BaP (1 µg/L and 10 µg/L) on gills of the pearl oyster Pinctada martensii using combined metabolomic and proteomic approaches. At the metabolome level, the high concentration of BaP mainly caused abnormal energy metabolism, osmotic regulation and immune response marked by significantly altered metabolites in gills. At the proteome level, both concentrations of BaP mainly induced signal transduction, transcription regulation, cell growth, stress response, and energy metabolism. Overall, the research demonstrated that the combination of proteomic and metabolomic approaches could provide a significant way to elucidate toxic effects of BaP on P. martensii.

Evaluation of the impact of bioaccumulation of PAH from the marine environment on DNA integrity and oxidative stress in marine rock oyster (Saccostrea cucullata) along the Arabian sea coast

Marine pollution due to oil spills is of great concern globally for their impact on the health of marine ecosystems. We assessed the genotoxic effects and oxidative stress due to genotoxic pollutants accumulated from the ambient marine environment in the tissues of marine rock oyster, Saccostrea cucullata along the Arabian Sea coast around Goa, India. The extent of DNA damage in S. cucullata was determined by comet assay as variation of comet parameter: mean % tail DNA along the coast with respect to that at the reference site (Tiracol, Goa, India). In addition, the oxidative stress responses of rock oysters exposed to marine pollutants such as polycyclic aromatic hydrocarbons (PAHs) were assessed as a function of variation in antioxidant enzyme activities such as glutathione-s-transferase (GST), catalase (CAT) and superoxide dismutase (SOD) along the coast. Spearman correlation analysis showed significant correlation between different components of PAHs (viz., 2-3-PAH, 4-6-PAH and oxy-PAH) in the tissues of the rock oysters and the antioxidant enzyme activities. The antioxidant enzyme activities in S. cucullata increased with increasing concentrations of PAHs in tissues in the following order of sampling sites: Tiracol < Arambol < Betul < Velsao. Among the PAHs, oxy-PAH was found to be most predominant in causing DNA damage in S. cucullata. These results provide an insight into environmental genotoxicity and oxidative stress induced by PAHs along the Arabian Sea coast, India.

Dynamic responses of antioxidant enzymes in pearl oyster Pinctada martensii exposed to di(2-ethylhexyl) phthalate (DEHP)

Di(2-ethylhexyl) phthalate (DEHP) is recognized as one of the most ubiquitous contaminants in marine environments and causes adverse effects on the health of marine organisms. The purpose of this study was to investigate the toxic effects of DEHP on the pearl oyster Pinctada martensii. The Pinctada martensii was exposed to 0.0, 0.5, 2, 8, or 32mgL^-1 DEHP for 7 and 10days using parameters of antioxidant. Antioxidant indicators included levels of superoxide dismutase (SOD), catalase (CAT), glutathione (GSH), peroxidase (POD), and total antioxidant capacity (T-AOC) in the gills and hepatopancreas of Pinctada martensii for 7 and 10days. Besides, we used the lowest observed effect concentration (LOEC) of five enzyme activities in different tissues of Pinctada martensii for 7 and 10days to compare sensitivity. The results showed that the gills were more sensitive than the hepatopancreas of Pinctada martensii and that GSH activity in the gills and CAT activity in the hepatopancreas might be suitable biomarkers after 7days of DEHP exposure. After 10days of DEHP exposure, the GSH activity and CAT activity in the gills and SOD activity in the hepatopancreas could be regarded as biomarkers. Compared to the LOEC, GSH activity in the gills and CAT activity in the hepatopancreas after 7days of DEHP exposure were more sensitive than any other biomarkers. In addition, after 10days of DEHP exposure, GSH activity in the gills and hepatopancreas were much more sensitive than other activities. In conclusion, GSH activity demonstrated its potential to be used as a biomarker for the monitoring of DEHP pollution in the marine environment.

Aryl hydrocarbon receptor (AHR): "pioneer member" of the basic-helix/loop/helix per-Arnt-sim (bHLH/PAS) family of "sensors" of foreign and endogenous signals

The basic-helix/loop/helix per-Arnt-sim (bHLH/PAS) family comprises many transcription factors, found throughout all three kingdoms of life; bHLH/PAS members "sense" innumerable intracellular and extracellular "signals" - including endogenous compounds, foreign chemicals, gas molecules, redox potential, photons (light), gravity, heat, and osmotic pressure. These signals then initiate downstream signaling pathways involved in responding to that signal. The term "PAS", abbreviation for "per-Arnt-sim" was first coined in 1991. Although the mouse Arnt gene was not identified until 1991, evidence of its co-transcriptional binding partner, aryl hydrocarbon receptor (AHR), was first reported in 1974 as a "sensor" of foreign chemicals, up-regulating cytochrome P450 family 1 (CYP1) and other enzyme activities that usually metabolize the signaling chemical. Within a few years, AHR was proposed also to participate in inflammation. The mouse [Ah] locus was shown (1973-1989) to be relevant to chemical carcinogenesis, mutagenesis, toxicity and teratogenesis, the mouse Ahr gene was cloned in 1992, and the first Ahr(-/-) knockout mouse line was reported in 1995. After thousands of studies from the early 1970s to present day, we now realize that AHR participates in dozens of signaling pathways involved in critical-life processes, affecting virtually every organ and cell-type in the animal, including many invertebrates.