Measurement of p-nitrophenyl acetate esterase activity (EA), total antioxidant capacity (TAC), total oxidant status (TOS) and acetylcholinesterase (AChE) in gills and digestive gland of Mytilus galloprovincialis exposed to binary mixtures of Pb, Cd and Cu

Reductive stress and cytotoxicity in the swollen river mussel (Unio tumidus) exposed to microplastics and salinomycin

Multistress effects lead to unpredicted consequences in aquatic ecotoxicology and are extremely concerning. The goal of this study was to trace how specific effects of the antibiotic salinomycin (Sal) and microplastics (MP) on the bivalve molluscs are manifested in the combined environmentally relevant exposures. Unio tumidus specimens were treated with Sal (0.6 μg L-1), MP (1 mg L-1, 2 μm size), and both at 18 °C (Mix) and 25 °C (MixT) for 14 days. The redox stress and apoptotic enzyme responses and the balance of Zn/Cu in the digestive gland were analyzed. The shared signs of stress included a decrease in NAD+/NADH and Zn/Cu ratios and lysosomal integrity and an increase in Zn-metallothioneins and cholinesterase levels. MP caused a decrease in the glutathione (GSH) concentration and redox state, total antioxidant capacity, and Zn levels. MP and Mix induced coordinated apoptotic/autophagy activities, increasing caspase-3 and cathepsin D (CtD) total and extralysosomal levels. Sal activated caspase-3 only and increased by five times Cu level in the tissue. Due to the discriminant analysis, the cumulative effect was evident in the combined exposure at 18 °C. However, under heating, the levels of NAD+, NADH, GSH, GSH/GSSG and metallothionein-related thiols were decreased, and coordination of the cytosolic and lysosomal death stimuli was distorted, confirming that heating and pollution could exert unexpected synergistic effects on aquatic life.

Neurotoxic effects of chloroquine and its main transformation product formed after chlorination

Pharmaceutical transformation products (TPs) generated during wastewater treatment have become an environmental concern. However, there is limited understanding regarding the TPs produced from pharmaceuticals during wastewater treatment. In this study, chloroquine (CQ), which was extensively used for treating coronavirus disease-19 (COVID-19) infections during the pandemic, was selected for research. We identified and fractionated the main TP produced from CQ during chlorine disinfection and investigated the neurotoxic effects of CQ and its main TP on zebrafish (Danio rerio) embryos. Halogenated TP353 was observed as one of the main TPs produced from CQ during chlorine disinfection. Zebrafish embryos test revealed that TP353 caused higher neurotoxicity in zebrafish larvae, as compared to the CQ, and that was accompanied by significantly decreased expression levels of the genes related to central nervous system development (e.g., gfap, syn2a, and elavl3), inhibited activity of acetylcholinesterase (AChE), reduced GFP fluorescence intensity of motor neuron axons in transgenic larvae (hb9-GFP), and reduced total swimming distance and swimming velocity of larvae during light-dark transition stimulation. The results of this study can potentially be utilized as a theoretical reference for future evaluations of environmental risks associated with CQ and its related TPs. This work presents a methodology for assessing the environmental hazards linked to the discharge of pharmaceutical TPs after wastewater treatment.

Acute thiamethoxam exposure induces hepatotoxicity and neurotoxicity in juvenile Chinese mitten crab (Eriocheir sinensis)

The similar nervous system structure between crustaceans and insects and the high-water solubility of thiamethoxam can lead to the more severe toxicity of thiamethoxam to crustaceans. However, the effects of thiamethoxam on crustaceans are unclear. Therefore, a 96-h acute toxicity test was performed to explore the hepatotoxicity and neurotoxicity effects of thiamethoxam on Chinese mitten crab (Eriocheir sinensis) at concentrations 0 µg/L, 150 µg/L and 300 µg/L. The antioxidant and detoxification systems (including phases I and II) were significantly activated after exposure of juvenile crabs to thiamethoxam for 24 h in 300 µg/L group, whereas the toxic activation effect in 150 μg/L group was delayed. Moreover, a similar pattern was observed for the transcription levels of immune-related genes. Further analysis of inflammatory signaling pathway-related genes showed that thiamethoxam exposure with 300 µg/L for 24 h may induce a pro-inflammatory response through the NF-κB pathway. In contrast, the gene expression levels in 150 µg/L group were significantly upregulated compared with 0 µg/L group after 96 h. In addition, although the acute exposure of 150 μg/L thiamethoxam did not seem to induce significant neurotoxicity, the acetylcholinesterase activity was significantly decreased in 300 μg/L group after thiamethoxam exposure for 96 h. Correspondingly, thiamethoxam exposure with 300 µg/L for 24 h resulted in significantly downregulated transcriptional levels of synaptic transmission-related genes (e.g. dopamine-, gamma-aminobutyric acid- and serotonin-related receptors). Therefore, thiamethoxam may be harmful and cause potential toxic threats such as neurotoxicity and metabolic damage to crustaceans.

Tissue-specific assessment of oxidative status: Wild boar as a case study

In recent decades, there has been a fast-growing interest in using biomarkers of oxidative stress (BOS) in conservation programs of many vertebrate species. Biomarkers of oxidative stress can be measured in different biological samples (e.g., body fluids and tissues). However, since comparisons of the same battery of BOS among tissues of the same individual are scarce in the literature, the chosen target tissues regularly rely on arbitrary decisions. Our research aimed to determine if the oxidative status of free-ranging wild boar (Sus scrofa) naturally infected with Mycobacterium spp (etiological agent of tuberculosis, TB), varies depending on the sample where it was quantified. We compared antioxidant p-nitrophenyl esterase activity (EA), glutathione peroxidase (GPX) concentrations, and total oxidative status (TOS) in serum, lung, spleen, kidney, and muscle of 63 wild boar hunter-harvested in central Spain. Biomarkers of oxidative stress in serum had higher concentrations than in other tissues. The poor agreement between serum and other tissues highlights the importance of running complete BOS assessments in the same fluid or tissue. Further, low concentrations of BOS in tissues of TB-affected individuals were observed, and significant differences between healthy and sick boar were only detected in the serum of individuals developing mild TB and in the muscle of individuals with mild or severe disease status. However, all organs from wild boars affected with mild TB were not in oxidative imbalance compared to healthy control animals, suggesting that wild boars may cope well with TB. Our data indicate that serum and other tissues can be used as BOS in field conservation programs to monitor wildlife population health. Still, context-specific validations are needed to determine the most appropriate samples to use.

Neurotoxicity of tetrabromobisphenol A and SiO2 nanoparticle co-exposure in zebrafish and barrier function of the embryonic chorion

Silicon dioxide nanoparticles (n-SiO₂) absorb tetrabromobisphenol A (TBBPA) and modify its bioavailability and toxicity in the aquatic phase; embryonic chorion is an efficient barrier against nanoparticles (e.g., SiO₂) and influences their toxicity. However, few studies have investigated developmental neurotoxicity in fish after co-exposure to TBBPA and n-SiO₂, especially considering the barrier function of the chorion. In the present study, zebrafish embryos were exposed to TBBPA (50, 100, and 200 μg/L) alone or in combination with n-SiO₂ (25 mg/L) until 24 or 120 h post fertilization (hpf), in the presence and absence of the chorion. The results confirmed that TBBPA exposure alone significantly downregulated the expression of neurodevelopment marker genes (mbp, alpha-tubulin, shha, and gfap), altered acetylcholinesterase activity and acetylcholine content, and affected locomotor behavior at different developmental stages. Moreover, the results indicated that n-SiO₂ promoted TBBPA-induced neurotoxic effects in zebrafish larvae at 120 hpf, including further repression of the transcription of CNS-related genes, disruption of the cholinergic system, and decrease in the average swimming speed under dark/light stimulation. However, scanning electron microscopy/energy dispersive spectroscopy analysis revealed that at 24 hpf, the embryonic chorion efficiently blocked n-SiO₂ and consequently decreased the bioaccumulation of TBBPA and TBBPA-induced neurotoxicity in dechorionated zebrafish embryos. Taken together, the results demonstrate that n-SiO₂ affected the bioavailability and neurodevelopmental toxicity of TBBPA, and their combined toxicity to zebrafish embryos was mitigated by embryonic chorion, which will facilitate risk assessment on n-SiO₂ and TBBPA and improve understanding the function of the fish embryonic chorion.

Source risk, ecological risk, and bioeffect assessment for polycyclic aromatic hydrocarbons (PAHs) in Laizhou Bay and Jiaozhou Bay of Shandong Peninsula, China

In order to incorporate the contribution of pollution sources to ecological risks into environmental monitoring, positive matrix factorization-risk quotient (PMF-RQ) was used to quantify the contribution of different PAH sources to ecological risks, which indicated that the unburned petroleum, vehicular emissions, and diesel combustion were the main sources of PAHs in Laizhou Bay and Jiaozhou Bay, and they were caused by petrochemical industry, maritime shipping, and urban traffic exhaust as the major sources of PAHs for ecological risk. Meanwhile, integrated biomarker response (IBR) and multi-biomarker pollution index (MPI) suggested that September was the most polluted month for PAHs in Laizhou Bay and Jiaozhou Bay and the pollution in Laizhou Bay was significantly higher than that in Jiaozhou Bay. This research was dedicated to explore the monitoring pattern for PAH pollution from the source to bioeffects, and it may have contributed a scientific support to monitoring and governance of marine PAH pollution.

Biochemical and respiratory parameters in a gastropod Radix balthica exposed to diclofenac

Diclofenac, an anti-inflammatory drug, is often detected in natural waters in the ng/L to μg/L range, posing a threat to aquatic organisms. The study focused on the effects of diclofenac in a gastropod mollusk Radix balthica. A 72-h exposure to environmentally relevant concentrations of diclofenac caused deviations from the baseline activities of the studied enzymes in the digestive gland of snails. Acetylcholinesterase activity was induced by the end of exposure, with the most pronounced increase at 3 μg/L. Results on glutathione-S-transferase activity were nonuniform, and no significant variations were observed in thiobarbituric acid reactive substances concentrations, indicating that diclofenac did not cause oxidative stress in the digestive gland of R. balthica at 0.04-4 μg/L range. Diclofenac lowered the oxygen consumption rate in snails in a concentration-dependent manner. At concentrations ≥0.9 μg/L, animals attempted to switch aquatic respiration to breathing air to regulate their metabolic needs. The study showed that diclofenac at environmentally relevant concentrations affected the fitness of R. balthica.

Imidacloprid and thiamethoxam affect synaptic transmission in zebrafish

Imidacloprid (IMI) and thiamethoxam (THM) are two commonly applied neonicotinoid insecticides. IMI and THM could cause negative impacts on non-target organisms like bees. However, the information about neurotoxicity of IMI and THM in fish is still scarce. Here we investigated the effects of IMI and THM on locomotor behavior, AChE activity, and transcription of genes related to synaptic transmission in zebrafish exposed to IMI and THM with concentrations of 50 ng L^-1 to 50,000 ng L^-1 at 14 day post fertilization (dpf), 21 dpf, 28 dpf and 35 dpf. Our results showed that IMI and THM significantly influenced the locomotor activity in larvae at 28 dpf and 35 dpf. THM elevated AChE activity at 28 dpf. The qPCR data revealed that IMI and THM affected the transcription of marker genes belonging to the synapse from 14 dpf to 35 dpf. Furthermore, IMI and THM mainly affected transcription of key genes in γ-aminobutyric acid, dopamine and serotonin pathways in larvae at 28 dpf and 35 dpf. These results demonstrated the neurotoxicity of IMI and THM in zebrafish. The findings from this study suggested that IMI and THM in the aquatic environment may pose potential risks to fish fitness and survival.

Effects of lincomycin hydrochloride on the neurotoxicity of zebrafish

Lincomycin hydrochloride is one of the commonly used drugs in clinic. However, it has many side effects on patients, and its mechanism is still poorly understood. In this study, 6 h post-fertilization (6 hpf) zebrafish embryos were exposed to several concentrations of lincomycin hydrochloride (15, 30, 60 μg/mL) for up to 24 or 96 hpf to detect their developmental toxicity and neurotoxicity, and to 6 days post-fertilization (6 dpf) to detect their behavioral toxicity. Our results showed that lincomycin hydrochloride could lead to embryonic head deformities (unclear ventricles, smaller ventricles, fewer new neurons). The studies showed that the frequency of spontaneous tail flick of zebrafish embryo increased at 24 hpf, and the lincomycin hydrochloride exposed zebrafish embryos showed increased heart rate, shorter body length, and yolk sac edema with severe pericardial edema at 96 hpf. The studies also showed that lincomycin hydrochloride increased oxidative stress level, Acetylcholinesterase (AChE) activity, ATPase activity and apoptosis in zebrafish larvae. In addition, the swimming behavior of zebrafish larvae decreased with the increase of lincomycin hydrochloride concentration, but the angular velocity and meandering degree increased, which might be due to the decreased activity of AChE and ATPase, as well as the decreased expression of genes related to neurodevelopment and neurotransmitter system, leading to the change of their motor behaviors. In summary, we found that lincomycin hydrochloride induced developmental toxicity and neurotoxicity in zebrafish larvae, contributing to a more comprehensive evaluation of the safety of the drug.

Antioxidant enzymes as biomarkers of Cu and Pb exposure in the ground spiders Lycosa terrestris and Pardosa birmanica

Heavy metal exposure induces oxidative stress in terrestrial organisms, which they counteract via activation of antioxidant biomarkers. The present study investigated the effects of copper (Cu) and lead (Pb) on the total antioxidant capacity (TAC) and antioxidant enzymes such as Catalase (CAT), Glutathione reductase (GR), Superoxide dismutase (SOD) and Glutathione peroxidase (GPX) in two spider species, namely Lycosa terrestris and Pardosa birmanica. The spiders were exposed to Cu and Pb separately (10 ppm) or in combination (10 ppm each) via two different exposure routes (i.e. food and soil) for 10, 20 and 40 days. The results showed that metal accumulation and antioxidant biomarker responses in spiders were metal- and species-dependent. Also, the levels of all antioxidant biomarkers increased significantly with increasing exposure time and metal load in the bodies of spiders via both exposure routes. The significant inhibition of TAC and antioxidant enzyme activities was only observed in single Pb treatment through soil exposure. In L. terrestris, the activities of detoxification enzymes and TAC were significantly enhanced on single Cu exposure than Pb via both exposure routes. However, in P. birmanica consistent variation among antioxidant parameters were observed depending on the metal load and exposure routes. The combined metal exposure caused more pronounced increase in the level of antioxidants compared to single metal exposure in both species, mainly via food exposure. These results suggest that the antioxidant enzymes and TAC are sensitive to single and combined metal exposure via both uptake routes. These data show that antioxidant parameters can be used potential biomarkers of oxidative stress associated with metal exposure and for monitoring environmental health using spiders as bioindicators.

Biomarkers of health and welfare: A One Health perspective from the laboratory side

A biomarker is any measurement reflecting an interaction between a biological system and a potential hazard, which may be chemical, physical, or biological. The One World, One Health concept established that human and animal health and the environmental state are highly interconnected, sharing common aspects that can be applied globally in these three components. In this paper, we review how the concept of One Health can be applied to biomarkers of health and welfare, with a special focus on five points that can be applied to any biomarker when it is expected to be used to evaluate the human, animal or environmental health. Three of these points are: (1) the different biomarkers that can be used, (2) the different sample types where the biomarkers can be analysed, and (3) the main methods that can be used for their measurement. In addition, we will evaluate two key points needed for adequate use of a biomarker in any situation: (4) a proper analytical validation in the sample that it is going to be used, and (5) a correct selection of the biomarker. It is expected that this knowledge will help to have a broader idea about the use of biomarkers of health and welfare and also will contribute to a better and more accurate use of these biomarkers having in mind their One Health perspective.

Toxic effects of oxine-copper on development and behavior in the embryo-larval stages of zebrafish

Oxine-copper (OxCu) is generally used as an agricultural pesticide and induces harmful effects on ecosystems. In this study, zebrafish was used to assess the aquatic toxicity of OxCu. To detect the effects on development, embryos of 6 h post-fertilization (hpf) were exposed to 10 μg/L, 20 μg/L, 40 μg/L OxCu for 18 h; meanwhile, to evaluate the effects on the behavior, larval fish at 6 days post-fertilization (dpf) were exposed to the same concentrations for 24 h. Here, we show that there are embryonic developmental defects, including abnormalities of head and trunk, brain ventricle atrophy, reduced newborn neurons, disordered neurons, increased intercellular space, concentrated cytoplasm, decreased heart beat and blood flow velocity, and developmental delay of the vascular system; in addition, some embryos exposed to the high concentration of OxCu degraded from the tail. We also found that the spontaneous tail coiling frequency and AChE enzyme activity were reduced, while oxidative stress (free radical damage) and cell apoptosis were significantly increased. Moreover, the expression of genes involved in neurodevelopment, vascular development and apoptosis were dysregulated in the OxCu exposed embryos in a concentration-dependent manner. Finally, we found that after exposure to OxCu, larval locomotor activity was decreased and accompanied by Parkinson-like (increased absolute turn angle and sinuosity) and anxiety-like (preferred to the central area) behavior. These results indicate that OxCu induces developmental toxicity and behavioral alterations by affecting AChE enzyme activity and oxidative stress. Our data present new proofs of OxCu toxicity and a warning for its application.

Genotoxic, cytotoxic, and neurotoxic responses in Anodonta cygnea after complex metal mixture treatment

Environmental effects associated with the release of various metals even at maximum permissible concentrations (MPC) to the aquatic ecosystems are evident. In the present work, time-dependent increase in accumulated metals amount in gills of Anodonta cygnea after exposure to complex metal (Zn 0.1, Cu 0.01, Ni 0.01, Cr 0.01, Pb 0.005, and Cd 0.005 mg/L, MPC accepted for the inland waters in EU) mixture at various time points (1, 2, 4, 7, 14, and 28 days) was investigated. Statistically significant increase of Cu and Cd was determined in mussel's gills after 7-day exposure, in comparison to control group; moreover, significantly elevated concentration of Cu was measured and after 14-day treatment (in comparison to control and pre-exposure group). Concentrations of five (Cu, Ni, Cr, Pb, and Cd) out of 6 investigated metals were statistically increased in gills tissue after 28-day treatment. Moreover, complex metal mixture has demonstrated tissue- and time-dependent genotoxicity (∑Gentox) and cytotoxicity (∑Cytox) responses in mussels. After 4-day exposure, there were found the highest ∑Gentox levels in gills cells and haemocytes. Two-day treatment of mussels resulted in the highest and statistically significant induction of ∑Cytox level (in gills). Furthermore, after short-term (4 days) exposure, statistically significant inhibition of AChE activity in hemolymph of metal mixture-exposed mussels, in comparison to control and pre-exposure group, was found. Comparison of investigated responses in different tissue of A. cygnea discloses new information about metal mixture (at MPC) impacts at different treatment time. According to the obtained geno- and cytotoxicity data, it is suggested that gills are more sensitive tissue. Environmentally relevant trace metal concentrations when existing in mixture are able to cause adverse effects in A. cygnea; therefore, biological effects at different levels of organism are expected as a realistic scenario.

Effects of nanoplastics on Mytilus galloprovincialis after individual and combined exposure with carbamazepine

Plastic pollution is a worldwide problem, highlighted by the fact that plastic materials degrade into nano-size particles (<100 nm), potentially becoming more bioavailable as well as a source of entry of other contaminants into organisms. The present study aimed to assess the effects of polystyrene nanoplastics (PS), individually or combined with carbamazepine (Cbz), on the Mediterranean mussel, Mytilus galloprovincialis. For this purpose, mussels were exposed for 96 h to a concentration range of PS (from 0.05 up to 50 mg L^-1), to Cbz (6.3 μg L^-1) alone and to the mixture of PS + Cbz (0.05 mg L^-1+ 6.3 μg L^-1). Molecular and biochemical biomarkers were assessed in the digestive glands, gills and haemolymph. The abundance of mRNA in the digestive glands and gills revealed significant alterations in the expression of genes associated with biotransformation, DNA repair, cell stress-response and innate immunity. Combined exposure of PS + Cbz induced significant downregulation in gene expression (e.g., hsp70) when compared to individual exposure. Total oxidant status increased in digestive glands after exposure to 0.5 mg L^-1 PS. Moreover, increased total antioxidant capacity and esterase activity were observed for PS 50 mg L^-1, in digestive glands and gills, respectively. The PS induced effects on neurotransmission, measured as inhibition of cholinesterase activity in haemolymph. Genotoxicity was found in haemocytes after exposure to PS, Cbz and their mixture. Moreover, lipid peroxidation was observed for 0.05 mg L^-1 PS exposure, showing that nanoplastics can induce oxidative damage. The present study demonstrated that PS, even at low concentrations, led to alterations on the assessed mussels' endpoints.

Exploring alternative biomarkers of pesticide pollution in clams

Acetylcholinesterase (AChE) is a reliable biomarker of pesticide exposure although in clams this activity is often very low or undetectable. Carboxylesterases (CEs) exhort several physiological roles, but also respond to pesticides. Searching for an AChE alternative, baseline CE activities were characterised in Ruditapes decussatus gills and digestive glands using five substrates suggestive of different isozymes. The long chain p-nitrophenyl butyrate and 1-naphthyl butyrate were the most sensitive. In the digestive gland, their kinetic parameters (V_max and K_m) and in vitro sensitivity to the organophosphorus metabolite chlorpyrifos oxon (CPX) were calculated. IC50 values, in the pM-nM range, suggest a high protection efficiency of CE-related enzymes towards CPX neurotoxicity. Other targeted enzymes were: activities of glutathione reductase, glutathione peroxidase, catalase, glutathione S-transferases (GSTs) and lactate dehydrogenase in gills and digestive glands. The high GSTs activity and CE/AChE ratio suggests that R. decussatus has a great capacity for enduring pesticide exposure.

Effects of omega-3 fatty acid supplementation on cigarette craving and oxidative stress index in heavy-smoker males: A double-blind, randomized, placebo-controlled clinical trial

BACKGROUND

Smoking-induced oxidative stress is thought to contribute to lower levels of omega-3 fatty acids in plasma and brain tissue. This lower level leads to impaired function in a dopaminergic system related to dependence and craving.

AIMS

The aim of this study was to evaluate the effects of omega-3 fatty acid supplementation on cigarette craving and oxidative stress index in heavy-smoker males.

METHODS

In this double-blind, randomized clinical trial, 54 heavy-smoker males (smoke ⩾20 cigarettes per day) were randomly selected to receive either five capsules of fish-oil-derived omega-3 fatty acid supplements ( n = 27, each 1 g capsule containing 180 mg of eicosapentaenoic acid and 120 mg of docosahexanoic acid) or a placebo ( n = 27) for 3 months. The psychometric evaluations (nicotine dependence and cigarette craving), biochemical markers (urinary cotinine, serum total antioxidant capacity and total oxidant status) and self-reported smoking status were used to assess the cigarette craving and oxidative stress index (oxidative stress index = total oxidant status/total antioxidant capacity).

RESULTS

There was a greater reduction in levels of nicotine dependence, cigarette craving and cigarettes smoked per day in the omega-3 fatty acid group compared to the placebo group, and the difference between the two groups increased from baseline to 3-month follow up. The model estimated that these differences were statistically significant ( p < 0.001, p < 0.001 and p < 0.001, respectively). Also, a significant decrease was observed in levels of total oxidant status ( p = 0.008) and oxidative stress index ( p = 0.011) in the omega-3 fatty acid group after intervention.

CONCLUSIONS

This study showed that high-dose omega-3 fatty acid supplementation appears to be useful in reducing cigarette craving and oxidative stress index in heavy-smoker males.

Alterations in haemolymph proteome of Mytilus galloprovincialis mussel after an induced injury

A proteomic and biochemical approach was performed to assess the effects of an induced muscle injury on the haemolymph of bivalve molluscs. For this purpose, Mytilus galloprovincialis were exposed to puncture of adductor muscle for three consecutive days, and their haemolymph proteome was then compared to healthy animals using 2-dimensional electrophoresis (2-DE) to identify proteins that differed significantly in abundance. Those proteins were then subjected to tandem mass spectrometry and 6 proteins, namely myosin, tropomyosin, CuZn superoxide dismutase (SOD), triosephosphate isomerase, EP protein and small heat shock protein were identified. SOD and tropomyosin changes were verified by spectrophotometric measurements and western blotting, respectively. As some of the proteins identified are related to muscular damage and oxidative stress, other biomarkers associated with these processes that can be evaluated by automatic biochemical assays were measured including troponin, creatine kinase (CK), and aspartate aminotransferase (AST) for muscle damage, and SOD, trolox equivalent antioxidant capacity (TEAC) and esterase activity (EA) for oxidative stress. Significantly higher concentrations of troponin, CK, AST, and TEAC were observed in mussels after puncture, being also possible biomarkers of non-specific induced damage.