Polystyrene microplastics mitigate the embryotoxic damage of metformin and guanylurea in Danio rerio

Effects of co-treatment with nano/microplastics and hydroxychloroquine on early development stages of Salmo trutta

As a potential remedy for COVID-19 treatment, hydroxychloroquine (HCQ) attracted considerable scholarly attention early in the pandemic. However, the ecological consequences of HCQ are not well understood, especially regarding their interactions with plastic waste such as nano-and microplastics (PS). This study aimed to investigate colloidal stability, bioaccumulation, and acute toxicity of carboxylate-modified polystyrene-based PS and HCQ, both alone and in combination, to Salmo trutta embryos and larvae. Spectroscopic properties of PS were found to change over time and to be affected by the presence of HCQ in the incubation water of organisms. Confocal microscopy showed that PS and HCQ, both alone and in combination, caused damage to the chorion of the exposed fish embryos. Particles of PS were detected in external tissues of larvae. The impact of the tested substances on fish was found to be dependent on the PS particle size, exposure duration, and the life stage of fish.

Toxic interactions between fluoxetine and microplastics in zebrafish embryonic development

The increasing use of antidepressants, especially fluoxetine (FLX), has resulted in their presence in aquatic environments due to wastewater discharges from municipal, industrial, and hospital sources. Simultaneously, microplastics (MPs) have been extensively studied in short-term (acute) exposures, showing adverse effects such as oxidative stress, behavioral alterations and neurotoxicity. However, the embryotoxic and teratogenic effects of these compounds, as well as their impacts on the survival, development, morphology, behavior, and reproduction of fish embryos in aquatic ecosystems, remain limited. This study evaluated the toxic effects of FLX (5, 40 ng/L), MPs (25, 100 particles/L) and their mixtures (FLX-MPs) at environmentally relevant concentrations. Microscopic characterization of fluorescent MPs was performed, and their presence was evaluated in Danio rerio embryos at 24 and 96 hpf, observing their localization in the chorion. In embryotoxicity and teratogenesis tests, FLX (100 ng/L) increased the rate of malformations, including deformations of the spine (CD), tail (TM) and hypopigmentation (H); MPs induced scoliosis (S), tail deformation (TM), incomplete hatching (IE) and a dose-dependent increase in malformations. FLX-MPs mixtures caused pericardial edema (PE), tail and spine deformation, delayed hatching (HR) and increased mortality. Oxidative damage analysis showed that FLX (40 ng/L) dose-dependently increased SOD and CAT activities, with an increase in cellular oxidation biomarkers (LPX, POX, HPX). Besides, MPs (100 particles/L) showed similar effects, with increased SOD, CAT, POX and HPX activities. The FLX-MPs mixture showed the most pronounced response. In gene expression, FLX (5, 40 ng/L) modulated genes such as bax, blc2 and casp3. MPs (25, 100 particles/L) induced the expression of bax, blc2, p53 and casp3. FLX-MPs mixtures (25 particles/L-40 ng/L, 100 particles/L-40 ng/L) expressed nfr1, p53, nfe2l2a and casp3. Histological damage revealed abnormal muscle fibers (AMF) and yolk sac edema (YSE) at 40 ng/L FLX, and lamellar fusion (LF) and scoliosis (S) in MPs (100 particles/L). Brain swelling (IBT) and neuromast loss (NL) were detected in FLX-MPs mixtures. In conclusion, both FLX and MPs and their combinations affect the embryonic development and physiological state of Danio rerio.

Unlocking the combined impact of microplastics and emerging contaminants on fish: A review and meta-analysis

Microplastics (MPs) possess unique adsorptive properties that render their surfaces prone to absorbing other contaminants. When interacting with these emerging contaminants, MPs may have unpredictable negative impacts on fish. Prior studies have primarily concentrated on the impact of single contaminants, while investigations into combined pollution have not received adequate attention. Therefore, research on combined pollution holds greater practical significance. The physiological indicators of fish affected by emerging contaminants and the mechanisms behind these effects are not yet fully clear. To address this issue, a meta-analysis was performed to evaluate the impact of combined pollution of MPs-containing emerging contaminants on various aspects of fish health, encompassing behavior, consumption, development, and reproduction, along with the assessment of oxidative stress and neurotoxicity of fish. The results of the meta-analysis indicated that combined pollution adversely impacted fish reproduction, development, oxidative stress, and neurotoxicity. Importantly, significant differences were observed between fish species regarding their susceptibility to function and oxidative stress. Further investigation into the mechanisms of the impact of combined pollution on fish revealed that the magnitude of this impact is closely associated with the characteristics of the MPs themselves. MPs with higher adsorption capacities tend to lead to more severe consequences, while the impact of MPs with lower adsorption capacities relies more on their toxicity. Nevertheless, a close correlation between the duration of exposure to combined pollution and the level of oxidative stress in fish was not identified. Through a systematic analysis of existing studies, this review not only explored the cumulative effects of combined pollution on fish but also highlighted the intricate nature of such pollution within aquatic ecosystems. It contributes to the growing body of knowledge on the subject and emphasizes the need for further research to unravel the complexities associated with the combined impact of MPs-containing emerging contaminants on aquatic life.

Ecotoxicological evaluation of chitosan biopolymer films particles in adult zebrafish (Danio rerio): A comparative study with polystyrene microplastics

To mitigate the environmental impact of microplastics (MPs), the scientific community has innovated sustainable and biodegradable polymers as viable alternatives to traditional plastics. Chitosan, the deacetylated form of chitin, stands as one of the most thoroughly investigated biopolymers and has garnered significant interest due to its versatile applications in both medical and cosmetic fields. Nevertheless, there is still a knowledge gap regarding the impact that chitosan biopolymer films (CBPF) may generate in aquatic organisms. In light of the foregoing, this study aimed to assess and compare the potential effects of CBPF on the gastrointestinal tract, gills, brain, and liver of Danio rerio against those induced by MPs. The findings revealed that both CBPF and MPs induced changes in the levels of oxidative stress biomarkers across all organs. However, it is essential to note that our star plots illustrate a tendency for CBPF to activate antioxidant enzymes and for MPs to produce oxidative damage. Regarding gene expression, our findings indicate that MPs led to an up-regulation in the expression of genes associated with apoptotic response (p53, casp3, cas9, bax, and bcl2) in all fish organs. Meanwhile, CBPF produced the same effect in genes related to antioxidant response (nrf1 and nrf2). Overall, our histological observations substantiated these effects, revealing the presence of plastic particles and tissue alterations in the gills and gastrointestinal tract of fish subjected to MPs. From these results, it can be concluded that CBPF does not represent a risk to fish after long exposure.

Assessing the impact of COVID-19 era drug combinations on hepatic functionality: A thorough investigation in adult Danio rerio

Current and thorough information on the ecotoxicological consequences of pharmaceuticals is accessible globally. However, there remains a substantial gap in knowledge concerning the potentially toxic effects of COVID-19 used drugs, individually and combined, on aquatic organisms. Given the factors above, our investigation assumes pivotal importance in elucidating whether or not paracetamol, dexamethasone, metformin, and their tertiary mixtures might prompt histological impairment, oxidative stress, and apoptosis in the liver of zebrafish. The findings indicated that all treatments, except paracetamol, augmented the antioxidant activity of superoxide dismutase (SOD) and catalase (CAD), along with elevating the levels of oxidative biomarkers such as lipid peroxidation (LPX), hydroperoxides (HPC), and protein carbonyl content (PCC). Paracetamol prompted a reduction in the activities SOD and CAT and exhibited the most pronounced toxic response when compared to the other treatments. The gene expression patterns paralleled those of oxidative stress, with all treatments demonstrating overexpression of bax, bcl2, and p53. The above suggested a probable apoptotic response in the liver of the fish. Nevertheless, our histological examinations revealed that none of the treatments induced an apoptotic or inflammatory response in the hepatocytes. Instead, the observed tissue alterations encompassed leukocyte infiltration, sinusoidal dilatation, pyknosis, fatty degeneration, diffuse congestion, and vacuolization. In summary, the hepatic toxicity elicited by COVID-19 drugs in zebrafish was less pronounced than anticipated. This attenuation could be attributed to metformin's antioxidant and hormetic effects.

Co-occurrence, toxicity, and biotransformation pathways of metformin and its intermediate product guanylurea: Current state and future prospects for enhanced biodegradation strategy

Accumulation of metformin and its biotransformation product "guanylurea" are posing an increasing concern due to their low biodegradability under natural attenuated conditions. Therefore, in this study, we reviewed the unavoidable function of metformin in human body and the route of its release in different water ecosystems. In addition, metformin and its biotransformation product guanylurea in aquatic environments caused certain toxic effects on aquatic organisms which include neurotoxicity, endocrine disruption, production of ROS, and acetylcholinesterase disturbance in aquatic organisms. Moreover, microorganisms are the first to expose and deal with the release of these contaminants, therefore, the mechanisms of biodegradation pathways of metformin and guanylurea under aerobic and anaerobic environments were studied. It has been reported that certain microbes, such as Aminobacter sp. and Pseudomonas putida can carry potential enzymatic pathways to degrade the dead-end product "guanylurea", and hence guanylurea is no longer the dead-end product of metformin. However, these microbes can easily be affected by certain geochemical cycles, therefore, we proposed certain strategies that can be helpful in the enhanced biodegradation of metformin and its biotransformation product guanylurea. A better understanding of the biodegradation potential is imperative to improve the use of these approaches for the sustainable and cost-effective remediation of the emerging contaminants of concern, metformin and guanylurea in the near future.

Polystyrene microplastics mitigate lead-induced neurotoxicity by reducing heavy metal uptake in zebrafish larvae

The combined pollution of lead (Pb) and polystyrene microplastics (PS-MPs) is common in aquatic environments. However, the combined neurotoxicity of these two pollutants is still poorly understood. In this study, zebrafish (Danio rerio) larvae were used to assess the combined neurotoxicity and mechanism of Pb and PS-MPs at environmentally relevant concentrations. The results showed that Pb (10 μg/L) induced abnormal behavior including significantly reduced movement distance, maximum acceleration, and average velocity (P < 0.05) along with altered expression of neurodevelopment-related genes (gap43 and α1-tubulin) (P < 0.05). PS-MPs (25 μg/L, 250 μg/L; diameter at 25 μm) co-exposure not only significantly reduced the concentration of Pb in the exposed solution (P < 0.01), but also decreased the uptake of Pb by downregulating the divalent metal transporter 1 gene (dmt1) (P < 0.01), thereby alleviating Pb-induced neurotoxicity. However, to demonstrate that PS-MPs alleviate the neurotoxicity of Pb by reducing Pb uptake, upregulation of dmt1 by addition of deferoxamine (DFO, an efficient iron chelator, 100 μM) significantly increased the Pb uptake and exacerbated neurotoxicity in zebrafish. In summary, our results demonstrated that PS-MPs alleviate Pb neurotoxicity by downregulating the mRNA level of dmt1 and decreasing the Pb uptake. This study provides a new insight into the combined neurotoxicity and underlying mechanisms of PS-MPs and Pb on zebrafish.

Independent and synergistic effects of microplastics and endocrine-disrupting chemicals on the reproductive social behavior of fathead minnows (Pimephales promelas)

Microplastics (MPs) have become an environmental concern in recent years, with most research focused on the physiological effects of exposure. Comparatively little consideration has been given to the potential behavioral impacts of exposure, which may also have fitness consequences for individuals. Moreover, MPs can serve as vectors for endocrine-disrupting chemicals and other locally co-occurring contaminants known to impair behavioral responses. This project aimed to determine whether MPs alone or in association with a common environmental EDC (17-alpha ethinyl estradiol; EE2) alter reproductive behavior and decision-making in fish. Male and female fathead minnows (Pimephales promelas) were exposed to MPs associated with either a low (10 ng/L; MPEE2 10) or high (50 ng/L, MPEE2 50) concentration of EE2, or MPs without EE2 (MPvirgin) for 30 days via a dietary feeding protocol. Behavioral trials were conducted on Day 31 to determine the effects of exposure on male-female social interactions. The expression of male sexually selected traits, including courtship, was unaffected by exposure. However, non-exposed females in all treatment groups trended toward discrimination against exposed males, which reached statistical significance for the MPEE2 50 group. Female fish exposed to MPs, alone or in association with EE2, were equally likely to approach and associate with non-exposed and exposed males. The results from this study suggest that MPs may alter social behavior in fishes and that the behavioral impacts of exposure may be more strongly pronounced in females than males. Such individual-level changes in fitness have the potential to impact population size, with downstream effects on the broader aquatic community.

Medicine designed to combat diseases of affluence affects the early development of fish. How do plastic microparticles contribute?

The incidence of diseases of affluence, such as diabetes mellitus, cardiovascular diseases, high blood pressure, and high cholesterol has been reported to rise. Consequently, the concentrations of residues of drugs designed to treat these diseases have been rising in water bodies. Moreover, the toxicity of these pharmaceuticals towards fish and other non-target organisms can be even enhanced by microplastic particles that are reportedly present in surface water. Therefore, the aim of this study was to describe the effects of three highly prescribed drugs, in particular metoprolol, enalapril, and metformin on fish early-life stages. Also, it was hypothesized that polystyrene microparticles will increase the toxicity of metoprolol to fish early-life stages. Embryonal acute toxicity tests on Danio rerio and Cyprinus carpio were carried out in order to describe the possible toxic effects of metoprolol, enalapril, and metformin. Also, the acute toxicity of polystyrene microparticles and the combination of metoprolol with polystyrene microparticles were tested on D. rerio embryos. Additionally, a 31-day long embryo-larval subchronic toxicity test was carried out with C. carpio in order to describe the long-term effects of low concentrations of metoprolol. The results of the study show that both metoprolol and enalapril have the potential to disrupt the early development of the heart in the embryonal stages of fish. Also, enalapril and metformin together with polystyrene microparticles seem to possibly disrupt the reproduction cycle and act as endocrine disruptors. Both pure polystyrene microparticles and the combination of them with metoprolol affect inflammatory processes in organisms. Additionally, metformin alters several metabolism pathways in fish early-life stages. The results of the study bring new evidence that even low, environmentally-relevant concentrations of pharmaceuticals have the potential to disrupt the early development of fish, particularly on a molecular level.

Health impact assessment after Danio rerio long-term exposure to environmentally relevant concentrations of metformin and guanylurea

The antidiabetic drug metformin (MET) and its metabolite guanylurea (GUA) have been frequently and ubiquitously detected in surface water. Consequently, there has been a consistent rise in studying the toxicity of MET and GUA in fish over the past decade. Nonetheless, it is noteworthy that no study has assessed the harmful effects both compounds might trigger on fish blood and organs after chronic exposure. Taking into consideration the data above, our research strived to accomplish two primary objectives: Firstly, to assess the effect of comparable concentrations of MET and GUA (1, 40, 100 μg/L) on the liver, gills, gut, and brain of Danio rerio after six months of flow-through exposure. Secondly, to compare the outcomes to identify which compound prompts more significant oxidative stress and apoptosis in organs and blood parameter alterations. Herein, findings indicate that both compounds induced oxidative damage and increased the expression of genes associated with apoptosis (bax, bcl2, p53, and casp3). Chronic exposure to MET and GUA also generated fluctuations in glucose, creatinine, phosphorus, liver enzymes, red and white blood count, hemoglobin, and hematocrit levels. The observed biochemical changes indicate that MET and GUA are responsible for inducing hepatic damage in fish, whereas hematological alterations suggest that both compounds cause anemia. Considering GUA altered to a more considerable extent the values of all endpoints compared to the control group, it is suggested transformation product GUA is more toxic than MET. Moreover, based on the above evidence, it can be inferred that a six-month exposure to MET and GUA can impair REDOX status and generate apoptosis in fish, adversely affecting their essential organs' functioning.

Effects of microplastics on the toxicity of co-existing pollutants to fish: A meta-analysis

Aquatic ecosystems are among the main destination for microplastics (MPs) in the environment. MPs that enter aquatic ecosystems can contribute to pollution together with other co-existing pollutants. However, whether such pollution results in higher or lower toxicity to fish than that caused by co-existing pollutants alone remains controversial. This study aimed at closing this research gap based on 1380 biological endpoints under the background of environmental MP concentrations collected from 55 laboratory studies. Overall, MPs in co-existing pollutant solutions significantly increased the toxicity to fish. Specifically, MPs elevated negative effects on the immune system, metabolism, and oxidative damage. Subgroup analysis indicated that changes in toxicity were related to fish life stage and MP size, but not to co-existing pollutant or MP type. Meta-regression analysis indicated that changes in toxicity were not related to the logarithm of the octanol-water partition coefficient (logKow) or exposure time. Finally, the differences between laboratory research and the actual aquatic environment were discussed from four aspects: MPs, co-existing pollutants, environmental factors, and experimental objects. Our study provides a basis for further understanding the potential impact of MPs on aquatic organisms from a combined pollution perspective. Moreover, our results can provide a reference for the conservation and management of aquatic ecosystems.