Microplastics aggravate the bioaccumulation and corresponding food safety risk of antibiotics in edible bivalves by constraining detoxification-related processes

Perfluorooctanoic acid (PFOA) disrupts cardiac performance of thick-shell mussel by inserting into the binding pocket of proliferator-activated receptor gamma and thereby causing lipid metabolism disorders

Invertebrates constitute the largest group of animals on Earth, accounting for approximately 97 % of all animal species. Although the heart of invertebrates could be a sensitive target for environmental pollution, potential cardiotoxicity for most contaminants has received little attention. In this study, perfluorooctanoic acid (PFOA) and thick-shell mussels (Mytilus coruscus) were used to investigate the effect of PFOA on cardiac performance and the potential underlying mechanisms. Heart beat monitoring demonstrated that four-week exposure to 0.5 and 5.0 μg/L of PFOA resulted in bradycardia and arrhythmia in thick-shell mussels. Moreover, considerably more triglyceride (TG) accumulation, higher lipoprotein lipase (LPL) and lipase (LPS) activities, and disruption of lipid metabolism-related genes were observed in the hearts of PFOA-exposed mussels. In addition, comparable adverse impacts were detected in mussels treated with proliferator-activated receptor gamma (PPARγ) agonist whereas the PFOA-induced effects were fully or partially alleviated by PPARγ antagonist. Furthermore, molecular docking and molecular dynamics simulation revealed a high binding affinity of PFOA to the PPARγ of 12 invertebrates, including thick-shell mussels. In general, our data suggest that PFOA may pose a severe threat to cardiac performance of invertebrate species by inserting into the binding pocket of PPARγ, and thereby causing cardiac lipid metabolism disorders.

Co-exposure to enrofloxacin and atrazine enhances the hepatotoxicity in Larimichthys crocea by targeting the hypothalamic-pituitary-thyroid and gut-liver axes

Enrofloxacin (ENR) and atrazine (ATZ) are common co-contaminants in marine environments. Although the immunosuppressive effects of ENR and the endocrine-disrupting properties of ATZ are well established, the combined effects of these pollutants on hepatotoxicity, particularly concerning the regulation of the hypothalamic-pituitary-thyroid (HPT) and gut-liver axes, remain poorly understood. In this study, Larimichthys crocea was exposed to ENR and ATZ at environmentally relevant concentrations, individually and in combination, to investigate the hepatotoxicity. Liver cell swelling, necrosis, oxidative stress, and elevated liver injury markers were observed, indicating hepatic damage, with co-exposure exacerbating liver injury. Decreased levels of thyrotropin-releasing hormone and thyroid-stimulating hormone, increased triiodothyronine and thyroxine, and altered expression of HPT axis-related genes demonstrated enhanced disruption of the HPT axis under co-exposure, which was strongly associated with oxidative stress and liver dysfunction. Molecular docking confirmed that ENR and ATZ inhibited thyroid hormone binding to target proteins, likely provoking the enhanced hepatotoxicity. Additionally, ATZ significantly intensified the intestinal bacterial disturbances induced by ENR, further aggravating hepatotoxicity through the gut-liver axis. This study is the first to reveal the increased risk associated with ENR and ATZ co-exposure, highlighting the need for attention to such co-contaminants.

Mixture Matters: Exploring the Overlooked Toxicity of Sulfamethoxazole and Trimethoprim in Aquatic Environments

Sulfamethoxazole (SMX) and trimethoprim (TRIM) are two antibiotics included in the third Watch list to be monitored in inland waters by the Water Framework Directive. However, their mixture (MIX) is overlooked and is especially concerning because it mirrors the real conditions in natural aquatic ecosystems. This study aimed to evaluate the toxic effects of environmentally relevant concentrations of SMX (150 μg/L), TRIM (30 μg/L), and MIX (150 μg/L SMX + 30 μg/L TRIM) in different standard species: Aliivibrio fischeri (bioluminescence inhibition), Escherichia coli ATCC 25922 (growth inhibition), Lemna minor (growth inhibition and biochemical biomarkers), Daphnia magna (immobilization/mortality, reproductive effects, and biochemical biomarkers), and Danio rerio (survival, hatchability, abnormalities, and biochemical biomarkers). Considering all the parameters evaluated, and using the Independent Action model and the antibiotics ecotoxicological assessment approach, the results reveal that: (i) all antibiotics affect the bacteria A. fischeri and E. coli differently, causing a pronounced E. coli inhibition growth; (ii) SMX and MIX were slightly toxic to D. magna (after 48 h) and D. rerio (after 96 h), and moderately toxic to L. minor (after 7 days) and D. magna (after 10 days); (iii) TRIM was slightly toxic to all organisms tested, except for L. minor, which exhibited moderate toxicity; (iv) the interaction of the antibiotics in mixture varied significantly depending on the parameter; however, it revealed similar toxicity to SMX. Significant ecotoxicological data were obtained, clarifying the ecological risks of these antibiotics in aquatic ecosystems. Remaining vigilant regarding environmental contamination linked to levels of SMX and TRIM in surface waters is crucial. Assessing the combined impacts of multiple stressors is essential for prioritizing environmental safety and ecotoxicity assessments for antibiotics amidst climate change, preserving the health and integrity of aquatic ecosystems.

Unraveling the toxic trio: Combined effects of thifluzamide, enrofloxacin, and microplastics on Mytilus coruscus

The presence of pesticides, antibiotics, and microplastics in aquatic environments poses a significant threat because of their persistence and potential harm to aquatic life and human health. However, few studies have explored their combined effects on bioaccumulation and toxicity in edible bivalves. This study examined the bioaccumulation and toxicological impacts of thifluzamide (TF) and enrofloxacin (ENR) on oxidative stress, neurotoxicity, detoxification, and metabolism in Mytilus coruscus after 4 weeks of exposure at the environmental level. The findings indicated that coexposure to TF and ENR or the presence of microplastic polystyrene (PS) increased TF and ENR accumulation in mussels and caused oxidative damage, as evidenced by elevated catalase and glutathione transferase activities and increased malondialdehyde (MDA) levels. Notably, compared with single exposures, coexposure to PS+TF, PS+ENR, or TF+ENR generally increased the MDA content, reduced acetylcholinesterase activity, and increased detoxification gene expression. Metabolomic analysis revealed that TF, ENR, and PS, either alone or combined, significantly disrupted multiple metabolic pathways by altering levels of glycerophospholipids, eicosanoids, amino acids, and nucleotides. Coexposure particularly worsened glycerophospholipid and arachidonic acid metabolism disturbances. These results suggest that combined exposure to TF, ENR or PS exacerbated the ecotoxicological effects of TF and ENR on M. coruscus. Taken together, the results of the present study could enhance our understanding of the environmental effects resulting from multipollutant interactions and their potential risks to seafood security.

Microplastics-exposure experience aggravates the accumulation of diarrhetic shellfish toxins (DSTs) in thick-shell mussel Mytilus coruscus through impairing detoxification processes

Possessing sessile filter-feeding lifestyle, bivalves are more susceptible to contamination by benthic phycotoxins such as the diarrhetic shellfish toxins (DSTs). Due to the prevalence of microplastics (MPs) in aquatic environments, bivalve that experienced MP-exposure are potentially at higher risk from exposure to DSTs-producing microalgae, however, little is known about the impacts of past MP-exposure experience on the accumulation of DSTs. In this study, taking polystyrene (PS) MPs and DSTs-producing Prorocentrum lima as representatives, the impacts of MP-exposure on DSTs accumulation were evaluated in the thick-shell mussel Mytilus coruscus. Our results demonstrated that mussels with MP-exposure experience accumulated markedly higher levels of DSTs in their digestive glands, which may result from a significant impairment of detoxification. In addition, although might exert their effects through different mechanisms, both MP- and/or P. lima-exposure aggravated the level of oxidative stress and led to significant histological lesion of the digestive glands, with the highest stress and lesion observed in mussels that exposed to P. lima after a 21-day MP-exposure. Collectively, our results indicate the risk of DSTs-contamination of bivalves could be markedly aggravated by the ubiquitous presence of MPs, which may pose a severe threat to human consumers and warrants upmost attention.

Enhanced degradation of exogenetic citrinin by glycosyltransferases in the oleaginous yeast Saitozyma podzolica zwy-2-3

The contamination by the toxin citrinin (CIT), produced by fungi, has been reported in agricultural foods and is known to be nephrotoxic to humans. In this study, we found that CIT could be effectively degraded by the oleaginous yeast Saitozyma podzolica zwy-2-3. Four genes encoding glycosyltransferases (GTs) in S. podzolica zwy-2-3 (SPGTs) were identified by evolutionary and structural analyses. The overexpression of SPGTs enhanced CIT degradation to 0.56 mg/L/h in S. podzolica zwy-2-3 by increasing ATP and glutathione (GSH) contents to oxidize CIT and scavenge reactive oxygen species (ROS). Besides, SPGTs promoted lipid synthesis by 9.3 % of S. podzolica zwy-2-3 under CIT stress. These results suggest that SPGTs in oleaginous yeast play a pivotal role in enhancing CIT degradation and lipid accumulation. These findings provide a valuable basis for the application of GTs in oleaginous yeast to alleviate CIT contamination in agricultural production, which may contribute to food safety.

Exposure to microplastics renders immunity of the thick-shell mussel more vulnerable to diarrhetic shellfish toxin-producing harmful algae

Despite both microplastics (MPs) and harmful algae blooms (HABs) may pose a severe threat to the immunity of marine bivalves, the toxification mechanism underlying is far from being fully understood. In addition, owing to the prevalence and sudden occurrence characteristics of MPs and HABs, respectively, bivalves with MP-exposure experience may face acute challenge of harmful algae under realistic scenarios. However, little is known about the impacts and underlying mechanisms of MP-exposure experience on the susceptibility of immunity to HABs in bivalve mollusks. Taking polystyrene MPs and diarrhetic shellfish toxin-producing Prorocentrum lima as representatives, the impacts of MP-exposure on immunity vulnerability to HABs were investigated in the thick-shell mussel, Mytilus coruscus. Our results revealed evident immunotoxicity of MPs and P. lima to the mussel, as evidenced by significantly impaired total count, phagocytic activity, and cell viability of haemocytes, which may result from the induction of oxidative stress, aggravation of haemocyte apoptosis, and shortage in cellular energy supply. Moreover, marked disruptions of immunity, antioxidant system, apoptosis regulation, and metabolism upon MPs and P. lima exposure were illustrated by gene expression and comparative metabolomic analyses. Furthermore, the mussels that experienced MP-exposure were shown to be more vulnerable to P. lima, indicated by greater degree of deleterious effects on abovementioned parameters detected. In general, our findings emphasize the threat of MPs and HABs to bivalve species, which deserves close attention and more investigation.

Exposure to polystyrene microplastics and perfluorooctane sulfonate disrupt the homeostasis of intact planarians and the growth of regenerating planarians

Microplastics (MPs) and perfluorinated compounds (PFAS) are widespread in the global ecosystem. MPs have the ability to adsorb organic contaminants such as perfluorooctane sulfonate (PFOS), leading to combined effects. The current work aims to explore the individual and combined toxicological effects of polystyrene (PS) and PFOS on the growth and nerves of the freshwater planarian (Dugesia japonica). The results showed that PS particles could adsorb PFOS. PS and PFOS impeded the regeneration of decapitated planarians eyespots, whereas the combined treatment increased the locomotor speed of intact planarians. PS and PFOS caused significant DNA damage, while co-treatment with different PS concentrations aggravated and attenuated DNA damage, respectively. Further studies at the molecular level have shown that PS and PFOS affect the proliferation and differentiation of neoblasts in both intact and regenerating planarians, alter the expression levels of neuronal genes, and impede the development of the nervous system. PS and PFOS not only disrupted the homeostasis of intact planarians, but also inhibited the regeneration of decapitated planarians. This study is the first to assess the multiple toxicity of PS and PFOS to planarians after combined exposure. It provides a basis for the environmental and human health risks of MPs and PFAS.

Nano-scale and micron-scale plastics amplify the bioaccumulation of benzophenone-3 and ciprofloxacin, as well as their co-exposure effect on disturbing the antioxidant defense system in mussels, Perna viridis

Plastics ranging from nano-scale to micron-scale are frequently ingested by many marine animals. These particles exhibit biotoxicity and additionally perform as vectors that convey and amass adsorbed chemicals within organisms. Meanwhile, the frequency of detection of the benzophenone-3 and ciprofloxacin can be adsorbed on plastic particles, then accumulated in bivalves, causing biotoxicity. To understand their unknown accumulative kinetics in vivo affected by different plastic sizes and toxic effect from co-exposure, several scenarios were set up in which the mode organism were exposed to 0.6 mg/L of polystyrene carrying benzophenone-3 and ciprofloxacin in three sizes (300 nm, 38 μm, and 0.6 mm). The live Asian green mussels were chosen as mode organism for exposure experiments, in which they were exposed to environments with plastics of different sizes laden with benzophenone-3 and ciprofloxacin, then depurated for 7 days. The bioaccumulation and depuration kinetics of benzophenone-3 and ciprofloxacin were measured using HPLC-MS/MS after one week of exposure and depuration. Meanwhile, their toxic effect were investigated by measuring the changes in six biomarkers (condition index, reactive oxygen species, catalase, glutathione, lipid peroxidation, cytochrome P450 and DNA damage). The bioconcentration factors in mussels under different exposure conditions were 41.48-111.75 for benzophenone-3 and 6.45 to 12.35 for ciprofloxacin. The results suggested that microplastics and nanoplastics can act as carriers to increase bioaccumulation and toxicity of adsorbates in mussels in a size-dependent manner. Overproduction of reactive oxygen species caused by microplastics and nanoplastics led to increased DNA damage, lipid peroxidation, and changes in antioxidant enzymes and non-enzymatic antioxidants during exposure. Marked disruption of antioxidant defenses and genotoxic effects in mussels during depuration indicated impaired recovery. Compared to micron-scale plastic with sizes over a hundred micrometers that had little effect on bivalve bioaccumulation and toxicity, nano-scale plastic greatly enhanced the biotoxicity effect.