Microplastics and Their Impact on Reproduction-Can we Learn From the C. elegans Model?

Exploring toxicological pathways of microplastics and nanoplastics: Insights from animal and cellular models

Microplastics (MPs) and nanoplastics (NPs) represent an emerging issue for human and animal health. This review critically examines in vitro and in vivo studies to elucidate their mechanisms of action and toxicological effects. Key objectives included: providing a comprehensive overview of MP-NPs studies in literature, assessing experimental conditions relative to real environmental scenarios, and identifying toxicological pathways at the molecular level. The findings revealed significant progress in understanding MP-NPs impacts. In particular, it has been observed the promotion of inflammation, oxidative stress, apoptosis, autophagy, and endoplasmic reticulum (ER) stress via specific signaling axes. Reproductive toxicity emerged as the primary research focus, particularly in male models, whereas effects on gastrointestinal, neurological, and cardiovascular systems were insufficiently studied, especially for the molecular pathways affected. Most studies disproportionately focused on polystyrene particles, neglecting other prevalent polymers such as polyethylene and polypropylene. Furthermore, reliance on synthetic microspheres and non-realistic experimental concentrations limits relevance to real-world conditions. Limited long-term exposure studies further constrain the understanding of MP-NPs persistence and risks. In view of this, future research should integrate environmentally relevant conditions for particles doses, size and composition, long-term exposure assessments, and advanced methodologies such as omics and computational modeling. In addition, therapeutic interventions targeting oxidative and ER stress, inflammation and apoptosis may be an excellent solution to mitigate MP-NPs toxicity. At the same time, a standardized global approach is needed to fully understand the risks posed by MP-NPs, attempting to safeguard public and environmental health.

Distinct responses of Caenorhabditis elegans to polyethylene microplastics and plant secondary metabolites

Soil worms are among the most abundant and functionally diverse soil animals. However, they have been largely overlooked in studies on microplastic (MP) toxicity. MPs and plant secondary metabolites (PSMs) are ubiquitous in soil due to plant litter decomposition and heavy MP contamination, inevitably interacting and exerting combined toxicity on soil organisms. However, little research has been conducted on their joint effects. This study investigates the individual and combined toxic effects of polyethylene (PE) MPs and three PSMs (glycyrrhizic acid, tannic acid, and matrine) on the model organism Caenorhabditis elegans. Physiological and biochemical responses were assessed using fluorescence microscopy, image analysis, and statistical methods. After 42 h of exposure to PE MPs and/or PSMs, worm growth and development were negatively impacted. Under experimental conditions, matrine and PE MPs synergistically inhibited worm growth, exacerbated neurological damage, and induced oxidative stress. In contrast, glycyrrhizic acid and tannic acid alleviated PE MP-induced growth inhibition, mitigated oxidative stress, and demonstrated antioxidant properties that counteracted oxidative damage. This study offers new insights into the combined effects of MPs and PSMs in soil ecosystems, contributing to ecological risk assessments and pollution management strategies.

Single and Synergistic Effects of Microplastics and Difenoconazole on Oxidative Stress, Transcriptome, and Microbiome Traits in Honey Bees

Microplastics (MPs) and pesticides are identified as two environmental pollutants. In the present study, we showed evidence of toxic effects on honey bees from chronic oral exposure to food containing difenoconazole alone (Dif) and in a binary mixture with polystyrene (PS)-MPs (Dif + PS). We observed a disrupted gut microbial community structure in bees after difenoconazole exposure, and the gut microbiota structure richness increased at the phylum and genus levels in Dif + PS group. Transcriptomic analysis revealed that difenoconazole exposure caused 98 differentially expressed genes (DEGs), while 41 DEGs were identified in Dif + PS group. PS-MPs seemed to mitigate oxidative damage and changes in the transcriptome profile in honey bees caused by difenoconazole to some extent. However, coexposure increased the disordered microbial community composition. Our study highlights the importance of investigating possible additive and synergic activities between stressors to comprehensively understand the effects of pollutants on pollinating insects.

Exploring the potential protective role of anthocyanins in mitigating micro/nanoplastic-induced reproductive toxicity: A steroid receptor perspective

Microplastics and nanoplastics (MPs/NPs) are ubiquitous environmental pollutants that act as endocrine-disrupting chemicals (EDCs), raising significant concerns about their impact on human health. Research highlights the hazardous effects of MPs/NPs on both male and female reproductive systems, influencing germ cells, embryo development, and progeny. Additionally, studies show that MPs/NPs affect the gene expression of anabolic steroid hormones in vitro and in vivo, inducing reproductive toxicity through mechanisms such as oxidative stress and inflammation. Considering these adverse effects, identifying natural compounds that can mitigate the toxicity of MPs/NPs is increasingly important. Plants offer a wealth of antioxidants and anti-inflammatory compounds that can counteract these harmful effects. Among these, anthocyanins, natural colorants responsible for the vibrant hues of fruits and flowers, exhibit a wide range of biological activities, including antioxidant, anti-inflammatory, and anti-neoplastic properties. Moreover, anthocyanins can modulate sex hormone levels and alleviate reproductive toxicity. Cyanidin-3-glucoside (C3G), one of the most extensively studied anthocyanins, shows promise in reducing reproductive toxicity, particularly in females, and in protecting male reproductive organs, including the testis and epididymis. This protective effect is believed to result from its interaction with steroid receptors, specifically the androgen and estrogen receptors (ERs). These findings highlight the need to explore the mechanisms by which anthocyanins mitigate the reproductive toxicity caused by MPs/NPs. This review provides novel insights into how natural compounds can be leveraged to lessen the impact of environmental contaminants on human health, especially concerning reproductive health.

Physiological impact of secondary nanoplastics on aquatic inhabitants in special reference to immunotoxicity

Nanoplastic (NP) pollution poses serious health hazards to aquatic ecosystems, impacting various physiological systems of aquatic organisms. This review examines the complex interplay between NPs and different physiological systems. In the digestive system, NPs downregulate the hsp70-like gene in Mytilus galloprovincialis, leading to decreased metabolic processes and impaired digestion. Neural system exposure to NPs induces abnormal expression of genes like neurogenin1, GFAP, FBJ murine osteosarcoma viral oncogene, GAP-43, synapsin IIa, apoptosis regulator a, Bcl2 and Caspase a, and apoptosis-related cysteine peptidase. These genes play a crucial role in neurodevelopment, synaptic function and apoptosis regulation, potentially impacting neurobiology and cancer biology. NPs also affect reproduction, including gametogenesis, spawning, fertilization, embryogenesis and larval survivability. In the respiratory system, treatment with these causes inflammation in the lungs and gills, resulting in respiratory dysfunction. Moreover, this review investigates the complex interaction between NPs and the immune systems of both invertebrates (e.g., molluscs, arthropods, echinoderms) and vertebrates (e.g., zebrafish). NPs-induced alterations in immune cell function heightened the susceptibility to pathogens and disrupted immune signalling pathways. Subcellular inflammatory responses have been characterized by the secretion of inflammation-promoting and chemotactic cytokines such as irg1l, interleukin 1, interferon, interleukin 6, C-C motif chemokine ligand 20a and tumour necrosis factor. The assessment of the combined effects of NPs and other xenobiotics highlighted their possible synergistic impacts on aquatic fauna and the environment. This comprehensive review emphasizes the urgent need for further research to understand the cumulative effects of NPs on organism health and fitness across multiple physiological systems.

Emerging contaminants in the Mediterranean Sea endangering Lebanon's Palm Islands Natural Reserve

The Mediterranean Sea is an intercontinental marine environment renowned for its biodiversity and ecological significance. However, it is also one of the most polluted seas globally with significant levels of microplastics and heavy metals among other emerging contaminants. In Lebanon, inadequate waste management infrastructure and unregulated industrial discharges have exacerbated water quality deterioration by introducing these complex contaminants into surface and seawater. The Palm Islands Natural Reserve in Lebanon is a UNESCO-designated marine protected area and home to endangered species. However, the reserve faces significant threats from pollution, including heavy metals and microplastics, exacerbated by nearby Tripoli's escalating contamination. Plasticisers, particularly phthalates, are recognized for their hormone-disrupting effects, and heavy metals like cadmium, lead, and arsenic pose severe eco-toxicological risks. This study investigates the levels of heavy metals and phthalates in water and sediments from the Palm Islands. Samples were collected from different locations within the reserve, and heavy metals and phthalates were detected, including chromium (13.58 to 19.28 μg L-1), arsenic (2.05 to 5.04 μg L-1), cadmium (1.27 to 3.04 μg L-1), and lead (0.92 to 2.88 μg L-1). Cadmium levels exceeded the permissible limits set by environmental regulatory bodies, highlighting an urgent pollution problem. Phthalates, including DEP and DEHP, were also detected in concentrations of 7.12-10.25 μg L-1 for DEP and 38.47-56.12 μg L-1 for DEHP raising concerns over their potential eco-toxicological impact on marine species. Our research underscores the need for comprehensive environmental monitoring, better waste management infrastructure, and stricter regulatory measures to address pollution in Lebanon's coastal ecosystems.

Emission of fibres from textiles: A critical and systematic review of mechanisms of release during machine washing

Research about health and environmental impacts of pollution caused by natural and plastic fibres is increasing, however, the role of textile characteristics in microfibre release during washing remains poorly understood. Given that machine washing is thought to be the main contributor to microfibre pollution, we systematically and critically reviewed previous publications looking at how textile features affect fibre emissions during washing. We examined the evidence related to findings from previous studies based on their research aims, ability to control variables that could confound results, use of procedural blanks and controls, and statistical methodologies. We observed that small-scale laboratory equipment frequently used to evaluate microfibre release (e.g. Gyrowash) generates significantly more fibres than domestic washing machines and should not be used to generate environmental estimations. Our findings have implications for ecotoxicology and risk assessment, particularly regarding the overlooked role of natural and cellulosic fibres. While synthetic fibres are widely recognised as the dominant form of microplastic in the environment, environmental surveys often report larger numbers of natural and cellulosic fibres. These fibres, however, account for only 18 % of those tested in the experiments analysed, indicating the need for further research to understand the underlying causes of their release. We concluded that although many textile characteristics are perceived as having an impact on fibre release, 81 % of studies failed to demonstrate clear evidence of the findings associated with such impacts. This work highlights the need for robust experiments to clarify these gaps, which could then allow the development of textiles with minimised shedding potential. We propose a stepwise approach to first build a foundational understanding of how individual washing parameters and textile features influence fibre release, followed by exploring the complexity of how the interaction between these variables impacts emissions.

Activated hedgehog and insulin ligands by decreased transcriptional factor DAF-16 mediate transgenerational nanoplastic toxicity in Caenorhabditis elegans

In Caenorhabditis elegans, transcriptional factor DAF-16 in insulin signaling pathway played important role in regulating transgenerational nanoplastic toxicity. Activation of insulin signals mediated transgenerational toxicity of polystyrene nanoparticle (PS-NP) by inhibiting DAF-16. Among identified germline ligands, expression of wrt-3 encoding hedgehog ligand was increased by RNAi of daf-16 in PS-NP exposed C. elegans. In PS-NP exposed C. elegans, expressions of 4 other germline hedgehog ligand genes and 10 hedgehog receptor genes were increased by daf-16 RNAi. Among these candidate genes, expressions of hedgehog ligand genes (grl-15, grl-16, qua-1, and wrt-1) and hedgehog receptor genes (ptr-23, scp-1, ptd-2, and ncr-1) could be increased by PS-NP (1-100 μg/L), and their transgenerational expressions were observed after PS-NP exposure. RNAi of grl-15, grl-16, qua-1, wrt-1, ptr-23, scp-1, ptd-2, and ncr-1 caused resistance to transgenerational PS-NP toxicity. In nematodes exposed to PS-NPs, RNAi of wrt-3, grl-15, grl-16, qua-1, and wrt-1 at parental generation (P0-G) inhibited expressions of ptr-23, scp-1, ptd-2, and ncr-1 in their offspring. Moreover, we observed increased expressions of insulin peptides genes (ins-3, ins-39, and daf-28) in PS-NP exposed daf-16(RNAi) nematodes, suggesting formation of feedback loop. We raise the molecular basis for formation of toxicity on multiple generations after nanoplastic exposure at P0-G.

Evaluation of the health impacts and deregulation of signaling pathways in humans induced by microplastics

This review assesses the diverse health risk factors associated with microplastic (MP) exposure and their impact on cellular signaling pathways. MPs induce chronic inflammation, oxidative stress, endocrine disruption, apoptosis, and immune dysregulation. They activate signaling pathways such as NF-κB, MAPK, and Nrf2, exacerbating inflammatory responses, oxidative damage, and hormonal imbalances. Understanding the interplay between MPs and signaling pathways is crucial for elucidating the mechanisms underlying MP-induced health effects. Effective risk assessment and management strategies are essential to mitigate the adverse health impacts of MPs on human populations. This research underscores the urgent need for interdisciplinary collaboration to safeguard human health and environmental sustainability in the face of rising MP pollution. In this paper, we also assess the risk factors caused by the microplastics in the pregnant women and the development of the fetus. This review explores the potential risks and challenges associated with MP exposure in newborn babies. It is quite concerning that microplastic particles were recently found in the placental tissue of newborn children for the first time. Although it is unclear how these tiny particles affect different organs, researchers believe that these tiny particles could potentially carry harmful chemicals or disrupt the developing immune system of the fetus. This review overall focuses on the impact of microplastic disrupting different signaling including reproductive health in humans.

Drosophila melanogaster as a tractable eco-environmental model to unravel the toxicity of micro- and nanoplastics

Micro- and nanoplastics have emerged as pervasive environmental pollutants with potential ecotoxicological impacts on various organisms, including the model organismDrosophila melanogaster. Here we comprehensively synthesize current research on the adverse effects of micro- and nanoplastics onDrosophila, highlighting key findings and identifying gaps in the literature. Micro- and nanoplastics can lead to physical damage, oxidative stress, inflammation, genotoxicity, epigenetic changes, apoptosis, and necrosis inDrosophila. Exposure to plastic debris affects nutrient absorption, energy metabolism, and reproductive health, often in a sex-specific manner. For instance, male flies are generally more susceptible to the toxic effects of polystyrene microplastics than female flies, showing greater mortality and metabolic disruptions. Furthermore, the combined exposure of plastics with heavy metals can exacerbate toxic effects, leading to enhanced oxidative stress, genotoxicity, and gut damage. While antagonistic effects have been identified particularly with silver compounds, where polystyrene microplastics reduce the bioavailability and toxicity of silver. The adverse effects of plastic particles onDrosophiladepend on size, with smaller particles penetrating deeper into tissues and eliciting stronger toxic responses. The chemical composition of the plastics and the presence of additives also play crucial roles in determining toxicity levels. Chronic exposure to low levels can be as harmful as acute high-dose exposure, highlighting the need for comprehensive, long-term studies to fully understand the ecological and biological impacts of plastic pollution.

A comprehensive review on the adverse effect of microplastics in the gastrointestinal system of Artemia sp

Microplastic waste in aquatic environments can lead to the mortality of large marine creatures, as it increases the risk of entanglement, strangulation, and starvation. Even though micro- and nano-plastics pose a hidden threat, researchers still know little about them. The food source is an essential factor in gut microbial diversity. A well-balanced intestinal microbiome impacts animal development and health. According to research, microplastics (MPs) like polyethylene (PE) and polystyrene (PS) affected the gut microbiota of Artemia sp., increasing their genetic diversity. Therefore, the present study examined the negative impacts of MPs within the gastrointestinal tract of Artemia sp., the primary protein source of fish. A comprehensive literature review showed that microplastic contamination and its additives impair environmental and aquatic health. The findings of this research show that MPs alter the gut microbiota of Artemia, which in turn affects fish and, ultimately, human health via a cascade of impacts.

Plastic pollution in terrestrial ecosystems: Current knowledge on impacts of micro and nano fragments on invertebrates

The increasing accumulation of small plastic particles, in particular microplastics (>1 µm to 5 mm) and nanoplastics (< 1 µm), in the environment is a hot topic in our rapidly changing world. Recently, studies were initiated to better understand the behavior of micro- and nanoplastics (MNP) within complex matrices like soil, as well as their characterization, incorporation and potential toxicity to terrestrial biota. However, there remains significant knowledge gaps in our understanding of the wide-extent impacts of MNP on terrestrial invertebrates. We first summarized facts on global plastic pollution and the generation of MNP. Then, we focused on compiling the existing literature examining the consequences of MNP exposure in terrestrial invertebrates. The diversity of investigated biological endpoints (from molecular to individual levels) were compiled to get a better comprehension of the effects of MNP according to different factors such as the shape, the polymer type, the organism, the concentration and the exposure duration. The sublethal effects of MNP are acknowledged in the literature, yet no general conclusion was drawn as their impacts are highly dependent on their characteristic and experimental design. Finally, the synthesis highlighted some research gaps and remediation strategies, as well as a protocol to standardize ecotoxicological studies.

Exploratory research on the multi-life stages mesh-type model of Caenorhabditis elegans in radiation ecology

To address the lack of effective dose quantification methods for the model organism Caenorhabditis elegans (C. elegans) in radiation ecology research, this study employs remeshing techniques to develop a comprehensive mesh-type model covering multi-life stages, from embryonic to larval (L1, L2, L3, L4) and adulthood. Using these models, Dose Coefficients (DC) for C. elegans in a soil environment under different exposure conditions (external and internal), material settings, and radioactive nuclides (³H, ⁶⁰Co, ⁹⁰Sr, 12⁹I, 1³1I, 1³⁴Cs, 1³⁷Cs) were calculated with the Monte Carlo toolkit Geant4. The results show that the difference in DC, when C. elegans material is set as either biological material or water, is within 5%. Under external exposure conditions, the impact of life stages on the population's average DC is minimal (with a maximum deviation not exceeding 10%). However, the distribution within the population varied significantly across life stages (under external exposure to 137Cs, the dispersion was 12.02% for adults and a considerably higher 60.30% for larvae). The earlier the life stage, the greater the variability in DC distribution within the C. elegans population. Furthermore, correlation analysis indicates a strong relationship between DC and life stages under internal exposure scenarios. The mesh-type model of C. elegans established in this study provides a valuable tool for radiation ecology research and has potential applications in broader research fields.

Comparison of Transgenerational Neurotoxicity between Pristine and Amino-Modified Nanoplastics in C. elegans

Increasing evidence has suggested that nanoplastic pollution has become a global concern. More importantly, transgenerational toxicity can be induced by nanoplastics at predicted environmentally relevant doses (ERDs). Considering that amino modification could increase nanoplastic toxicity, we compared transgenerational neurotoxicity between pristine polystyrene nanoparticle (PS-NP) and amino-modified PS-NP (NH2-PS-NP) in Caenorhabditis elegans. At 0.1-10 μg/L, NH2-PS-NP caused more severe transgenerational toxicity on locomotion and neuronal development. Accompanied with a difference in transgenerational neuronal damage, compared to PS-NP (10 μg/L), NH2-PS-NP (10 μg/L) induced more severe transgenerational activation of mec-4, crt-1, itr-1, and tra-3, which are required for the induction of neurodegeneration. Moreover, NH2-PS-NP (10 μg/L) caused more severe transgenerational inhibition in expressions of mpk-1, jnk-1, dbl-1, and daf-7 than PS-NP (10 μg/L), and RNA interference (RNAi) of these genes conferred susceptibility to the toxicity of PS-NP and NH2-PS-NP on locomotion and neuronal development. NH2-PS-NP (10 μg/L) further caused more severe transgenerational activation of germline ligand genes (ins-3, ins-39, daf-28, lin-44, egl-17, efn-3, and lag-2) than PS-NP (10 μg/L), and RNAi of these ligand genes caused resistance to the toxicity of PS-NP and NH2-PS-NP on locomotion and neuronal development. Our results highlighted more severe exposure risk of amino-modified nanoplastics at ERDs in causing transgenerational neurotoxicity in organisms.

Reproductive toxicity and related mechanisms of micro(nano)plastics in terrestrial mammals: Review of current evidence

Micro(nano)plastics (MNPs) have been detected in various ecological environments and are widely used due to their stable properties, raising widespread concern about their potential human reproductive toxicity. Currently, infertility affects approximately 10-30% of couples of reproductive age globally. MNPs, as environmental pollutants, have been shown to exhibit reproductive toxicity through intrinsic mechanisms or as carriers of other hazardous substances. Numerous studies have established that MNPs of varying sizes and types can penetrate biological barriers, and enter tissues and even organelles of organisms through four main routes: dietary ingestion, inhalation, dermal contact, and medical interventions. However, historical research on the toxic effects of MNPs on reproduction mainly focused on lower and aquatic species. We conducted an inclusive review of studies involving terrestrial mammals, revealing that MNPs can induce reproductive toxicity via various mechanisms such as oxidative stress, inflammation, fibrosis, apoptosis, autophagy, disruption of intestinal flora, endocrine disruption, endoplasmic reticulum stress, and DNA damage. In terrestrial mammals, reproductive toxicity predominantly manifests as disruption in the blood-testis barrier (BTB), impaired spermatogenesis, sperm malformation, sperm DNA damage, reduced sperm fertilizing capacity, compromised oocyte maturation, impaired follicular growth, granulosa cell apoptosis, diminished ovarian reserve function, uterine and ovarian fibrosis, and endocrine disruption, among other effects. Furthermore, MNPs can traverse the maternal-fetal interface, potentially impacting offspring reproductive health. To gain a comprehensive understanding of the potential reproductive toxicity and underlying mechanisms of MNPs with different sizes, polymer types, shapes, and carried toxins, as well as to explore effective protective interventions for mitigating reproductive damage, further in-depth animal studies, clinical trials, and large-scale epidemiological studies are urgently required.

Polystyrene nanoplastics cause reproductive toxicity in zebrafish: PPAR mediated lipid metabolism disorder

The ubiquitous presence of micro-and nanoplastics (MNPs) in the environment and everyday products has attracted attention due to their hazardous risks. However, the effects of MNPs on reproduction and the underlying mechanisms remain unclear. The present study investigated the impact of polystyrene (PS) nanoplastics of 80, 200 and 500 nm diameters on zebrafish reproduction at an environmentally relevant concentration of 0.5 mg/L. Exposure to PS delayed spermatogenesis and caused aberrant follicular growth, resulting in dysgenesis in F0 adults and impacting F1 embryo development. Notably, the reproductive toxicity exhibited size-dependency, with the 500 nm PS being the most detrimental. Combined analyses of transcriptomics and metabolomics in ovary tissue revealed that treatment with 500 nm PS affected the peroxisome proliferator-activated receptor (PPAR) signaling pathway, dysregulated lipid transport, binding and activity processes, and led to dysgenesis in zebrafish. Specifically, the ovulatory dysfunction induced by PS exposure resembled clinical manifestations of polycystic ovary syndrome (PCOS) and can be attributed to lipid metabolism disorder involving glycerophospholipid, sphingolipid, arachidonic acid, and alpha-linolenic acid. Collectively, our results provide new evidence revealing the molecular mechanisms of PS-induced reproductive toxicity, highlighting that MNPs may pose a risk to female reproductive health.

Using marine mussels to assess the potential ecotoxicological effects of two different commercial microplastics

Microplastics (MPs) in the aquatic environment pose a serious threat to biota, by being confounded with food. These effects occur in mussels which are filter-feeding organisms. Mussels from the genus Mytilus sp. were used to evaluate the ecotoxicological effects of two MPs, polypropylene (PP) and polyethylene terephthalate (PET), after 4 and 28-days. Measured individual endpoints were condition index and feeding rate; and sub-individual parameters, metabolism of phase I (CYP1A1, CYP1A2 and CYP3A4) and II (glutathione S-transferases - GSTs), and antioxidant defense (catalase - CAT). MPs decreased both condition index (CI) and feeding rate (FR). No alterations occurred in metabolic enzymes, suggesting that these MPs are not metabolized by these pathways. Furthermore, lack of alterations in GSTs and CAT activities suggests the absence of conjugation and oxidative stress. Overall, biochemical markers were not responsive, but non-enzymatic responses showed deleterious effects caused by these MPs, which may be of high ecological importance.

Size dependent ingestion and effects of microplastics on survivability, hematology and intestinal histopathology of juvenile striped catfish (Pangasianodon hypophthalmus)

Microplastic pollution is drastically increasing in aquatic ecosystems and it is assumed that different sizes of microplastics have diverse impacts on the physiology of aquatic organisms. Therefore, this study was intended to examine the ingestion and size specific effects of polyamide microplastic (PA-MP) on different physiological aspects such as growth, feed utilization, survivability, blood parameters and intestinal histopathology of juvenile striped catfish (Pangasianodon hypophthalmus). In a 28-day exposure, the fish were fed with different sized PA-MP with a concentration of 500 mg per kg of feed in order to simulate highly microplastic contaminated environment. Three different treatments were set for this experiment i.e. T1, 25-50 μm (smaller microplastic); T2, 300 μm-2 mm (larger microplastic); T3, (mixed) including a control (C); each had three replicates. The highest ingestion was recorded in the gastrointestinal tract (GIT) of fish exposed to smaller PA-MP treatments (T1 followed by T3). The results also showed compromised weight gain (WG; g), specific growth rate (SGR; %/day) and feed conversion ratio (FCR) with the exposure of PA-MP. Besides, survivability significantly reduced among treatments with the ingestion of smaller sized microplastic and found lowest in T1 (65.0 ± 5.0). In addition, the presence of PA-MP in feed negatively affected the concentration of hemoglobin and blood glucose. Similarly, smaller PA-MP caused most erythrocytic cellular and nuclear abnormalities; found highest in T1 that significantly different from other treatments (p < 0.05). Various histopathological deformities were observed in fish fed with PA-MP incorporated feed. The principal component analysis (PCA) showed that the toxicity and stress imparted by smaller PA-MP affected the survivability and blood parameters where larger PA-MP caused mild to severe abnormalities. Based on eigenvector values, the major abnormalities in intestine included occurrence of epithelium columnar degeneration (ECD: 0.402; PC1), hyperplasia of internal mucosa (HISM: 0.411; PC1), beheading of villi (BV: 0.323; PC1), atrophy of mucosa (AM: 0.322; PC1), tiny vacuoles in apical villi (TV: 0.438. PC2), crypt degeneration (CD: 0.375: PC2) and atrophy of goblet cell (AGC: 0.375; PC2). Therefore, it has been speculated that the size based PA-MP ingestion in the GIT interfered with the digestion and absorption as well as caused deformities that reflected negatively in survivability and hemato-biochemical parameters of juvenile striped catfish.

Photoaged polystyrene nanoplastics exposure results in reproductive toxicity due to oxidative damage in Caenorhabditis elegans

The increase of plastic production together with the incipient reuse/recycling system has resulted in massive discards into the environment. This has facilitated the formation of micro- and nanoplastics (MNPs) which poses major risk for environmental health. Although some studies have investigated the effects of pristine MNPs on reproductive health, the effects of weathered MNPs have been poorly investigated. Here we show in Caenorhabditis elegans that exposure to photoaged polystyrene nanoplastics (PSNP-UV) results in worse reproductive performance than pristine PSNP (i.e., embryonic/larval lethality plus a decrease in the brood size, accompanied by a high number of unfertilized eggs), besides it affects size and locomotion behavior. Those effects were potentially generated by reactive products formed during UV-irradiation, since we found higher levels of reactive oxygen species and increased expression of GST-4 in worms exposed to PSNP-UV. Those results are supported by physical-chemical characterization analyses which indicate significant formation of oxidative degradation products from PSNP under UV-C irradiation. Our study also demonstrates that PSNP accumulate predominantly in the gastrointestinal tract of C. elegans (with no accumulation in the gonads), being completely eliminated at 96 h post-exposure. We complemented the toxicological analysis of PSNP/PSNP-UV by showing that the activation of the stress response via DAF-16 is dependent of the nanoplastics accumulation. Our data suggest that exposure to the wild PSNP, i.e., polystyrene nanoplastics more similar to those actually found in the environment, results in more important reprotoxic effects. This is associated with the presence of degradation products formed during UV-C irradiation and their interaction with biological targets.

Combined effect of polystyrene nanoplastic and di-n-butyl phthalate on testicular health of male Swiss albino mice: analysis of sperm-related parameters and potential toxic effects

Plastics, especially polystyrene nanoplastic particles (PSNPs), are known for their durability and absorption properties, allowing them to interact with environmental pollutants such as di-n-butyl phthalate (DBP). Previous research has highlighted the potential of these particles as carriers for various pollutants, emphasizing the need to understand their environmental impact comprehensively. This study focuses on the subchronic exposure of male Swiss albino mice to PSNP and DBP, aiming to investigate their reproductive toxicity between these pollutants in mammalian models. The primary objective of this study is to examine the reproductive toxicity resulting from simultaneous exposure to PSNP and DBP in male Swiss albino mice. The study aims to analyze sperm parameters, measure antioxidant enzyme activity, and conduct histopathological and morphometric examinations of the testis. By investigating the individual and combined effects of PSNP and DBP, the study seeks to gain insights into their impact on the reproductive profile of male mice, emphasizing potential synergistic interactions between these environmental pollutants. Male Swiss albino mice were subjected to subchronic exposure (60 days) of PSNP (0.2 mg/m, 50 nm size) and DBP (900 mg/kg bw), both individually and in combination. Various parameters, including sperm parameters, antioxidant enzyme activity, histopathological changes, and morphometric characteristics of the testis, were evaluated. The Johnsen scoring system and histomorphometric parameters were employed for a comprehensive assessment of spermatogenesis and testicular structure. The study revealed non-lethal effects within the tested doses of PSNP and DBP alone and in combination, showing reductions in body weight gain and testis weight compared to the control. Individual exposures and the combination group exhibited adverse effects on sperm parameters, with the combination exposure demonstrating more severe outcomes. Structural abnormalities, including vascular congestion, Leydig cell hyperplasia, and the extensive congestion in tunica albuginea along with both ST and Leydig cell damage, were observed in the testis, underscoring the reproductive toxicity potential of PSNP and DBP. The Johnsen scoring system and histomorphometric parameters confirmed these findings, providing interconnected results aligning with observed structural abnormalities. The study concludes that simultaneous exposure to PSNP and DBP induces reproductive toxicity in male Swiss albino mice. The combination of these environmental pollutants leads to more severe disruptions in sperm parameters, testicular structure, and antioxidant defense mechanisms compared to individual exposures. The findings emphasize the importance of understanding the interactive mechanisms between different environmental pollutants and their collective impact on male reproductive health. The use of the Johnsen scoring system and histomorphometric parameters provides a comprehensive evaluation of spermatogenesis and testicular structure, contributing valuable insights to the field of environmental toxicology.

Toxicological impacts of microplastics on virulence, reproduction and physiological process of entomopathogenic nematodes

Microplastics have emerged as significant and concerning pollutants within soil ecosystems. Among the soil biota, entomopathogenic nematodes (EPNs) are lethal parasites of arthropods, and are considered among the most effective biological agents against pests. Infective juveniles (IJs) of EPNs, as they navigate the soil matrix scavenging for arthropod hosts to infect, they could potentially encounter microplastics. Howver, the impact of microplastics on EPNs has not been fully elucidated yet. We addressed this gap by subjecting Steinernema feltiae EPNs to polystyrene microplastics (PS-MPs) with various sizes, concentrations, and exposure durations. After confirming PS-MP ingestion by S. feltiae using fluorescent dyes, we found that the PS-MPs reduced the survival, reproduction, and pathogenicity of the tested EPNs, with effects intensifying for smaller PS-MPs (0.1-1 μm) at higher concentrations (105 μg/L). Furthermore, exposure to PS-MPs triggered oxidative stress in S. feltiae, leading to increased reactive oxygen species levels, compromised mitochondrial membrane potential, and increased antioxidative enzyme activity. Furthermore, transcriptome analyses revealed PS-MP-induced suppression of mitochondrial function and oxidative phosphorylation pathways. In conclusion, we show that ingestion of PS-MPs by EPNs can compromise their fitness, due to multple toxicity effects. Our results bear far-reaching consequences, as the presence of microplastics in soil ecosystems could undermine the ecological role of EPNs in regulating pest populations.

Comparison of reproductive toxicity between pristine and aged polylactic acid microplastics in Caenorhabditis elegans

Caenorhabditis elegans was employed as model to compare reproductive toxicity between pristine and aged polylactic acid microplastics (PLA-MPs). Aged PLA-MPs induced by UV irradiation showed degradation reflected by decrease in size and alteration in morphological surface. Aged PLA-MPs also exhibited some certain changes of chemical properties compared to pristine PLA-MP. Compared with pristine PLA-MPs, more severe toxicity on reproductive capacity and gonad development was detected in 1-100 μg/L aged PLA-MPs. Meanwhile, aged PLA-MPs caused more severe enhancement in germline apoptosis and alterations in expressions of ced-9, ced-4, ced-3, and egl-1 governing cell apoptosis. In addition, aged PLA-MPs resulted in more severe increase in expression of DNA damage related genes (cep-1, mrt-2, hus-1, and clk-2) compared to pristine PLA-MPs, and the alterations in expression of ced-9, ced-4, ced-3, and egl-1 in pristine and aged PLA-MPs could be reversed by RNAi of cep-1, mrt-2, hus-1, and clk-2. Besides this, enhanced germline apoptosis in pristine and aged PLA-MPs exposed animals was also suppressed by RNAi of cep-1, mrt-2, hus-1, and clk-2. Therefore, our results suggested the more severe exposure risk of aged PLA-MPs than pristine PLA-MPs in causing reproductive toxicity, which was associated with the changed physicochemical properties and DNA damage induced germline apoptosis.

Unraveling the threat: Microplastics and nano-plastics' impact on reproductive viability across ecosystems

Plastic pollution pervades both marine and terrestrial ecosystems, fragmenting over time into microplastics (MPs) and nano-plastics (NPs). These particles infiltrate organisms via ingestion, inhalation, and dermal absorption, predominantly through the trophic interactions. This review elucidated the impacts of MPs/NPs on the reproductive viability of various species. MPs/NPs lead to reduced reproduction rates, abnormal larval development and increased mortality in aquatic invertebrates. Microplastics cause hormone secretion disorders and gonadal tissue damage in fish. In addition, the fertilization rate of eggs is reduced, and the larval deformity rate and mortality rate are increased. Male mammals exposed to MPs/NPs exhibit testicular anomalies, compromised sperm health, endocrine disturbances, oxidative stress, inflammation, and granulocyte apoptosis. In female mammals, including humans, exposure culminates in ovarian and uterine deformities, endocrine imbalances, oxidative stress, inflammation, granulosa cell apoptosis, and tissue fibrogenesis. Rodent offspring exposed to MPs experience increased mortality rates, while survivors display metabolic perturbations, reproductive anomalies, and weakened immunity. These challenges are intrinsically linked to the transgenerational conveyance of MPs. The ubiquity of MPs/NPs threatens biodiversity and, crucially, jeopardizes human reproductive health. The current findings underscore the exigency for comprehensive research and proactive interventions to ameliorate the implications of these pollutants.

Metabolic equilibrium and reproductive resilience: Freshwater gastropods under nanoplastics exposure

Nanoplastics (NPs) have gained increasing attention due to their widespread presence in aquatic environments and potential adverse effects on organisms. The interaction between NPs and freshwater gastropods can lead to a range of physiological and reproductive disturbances. In this study, we investigated the adverse effects of NPs (two size: 20 nm and 100 nm; three concentrations: 0.5, 50 and 100 ppm) on energy metabolism and reproductive fitness in freshwater gastropods Lymnean stagnalis after 21 days exposure. Briefly, the condition index negatively correlated with increasing NPs concentrations for both sizes. Bioaccumulation revealed a concentration-dependent trend in the 100 nm group, and the highest accumulation appeared in the 100 ppm group, compared to all the rest groups. This phenomenon could be attributed to the larger surface area which facilitates stronger attachment to tissues, while smaller particles could be cleared more readily from body. Carbohydrate and protein reserves remained largely unaffected at all concentrations. However, 100 nm NPs triggered stress responses, increasing lipid production, and 20 nm NPs potentially interfered with mitochondrial function, affecting electron transport system activity. Despite the variations observed in lipid levels and energy cost, the ratio of available energy to energy cost remained stable across for both NPs sizes, and this resilience suggests that cellular energy allocation endured undisturbed, hinting at mechanisms that enable gastropods to maintain their metabolic equilibrium. Reproductively, NPL-exposed groups had fewer clutches, with clutches per collection time decreasing over time for both sizes. In terms of egg development, shell growth and hatching rates remained unaffected, suggesting resilience in aquatic ecosystems.In conclusion, this study underscores the substantial impact of NPs on freshwater gastropods, raising ecological and reproductive concerns. The intricate interplay between nanoparticle size, concentration, and physiological responses highlights the complexity of NPs interactions in aquatic ecosystems, necessitating further research and regulatory measures.

Polyethylene nanoplastics cause reproductive toxicity associated with activation of both estrogenic hormone receptor NHR-14 and DNA damage checkpoints in C. elegans

As the most commercial polymer, the polyethylene nanoparticle (PE-NP) has been discharged into the environment and poses potential risks to organisms. However, the possible reproductive toxicity of PE-NP and underlying mechanisms remain largely unknown. In this study, Caenorhabditis elegans was employed as the animal model to effects of PE-NP (100 nm) and their leachates on reproduction and underlying mechanisms. Nematodes were exposed to PE-NP at 0.1-100 μg/L from L1-larvae to adult day 1 (approximately 4.5 days). Both brood size and number of fertilized eggs in uterus were decreased by 10 and 100 μg/L PE-NP, but could not be affected by their leachates. In addition, number of mitotic cells, length, and area of gonad were reduced by 10 and 100 μg/L PE-NP, but were not altered by their leachates. Accompanied with alteration in expressions of genes (egl-1, ced-9, ced-4, and ced-3) governing cell apoptosis, germline apoptosis was enhanced by PE-NP. Meanwhile, DNA damage was involved in the enhancement germline apoptosis after PE-NP exposure. PE-NP further increased expression of nhr-14 encoding estrogenic hormone receptor, and RNAi of nhr-14 suppressed PE-NP reproductive toxicity. Moreover, RNAi of nhr-14 decreased expression of egl-1, ced-4, ced-3, and mrt-2 in PE-NP exposed nematodes. Therefore, exposure to PE-NPs rather than in their leachates potentially caused reproductive toxicity by activating both estrogenic hormone receptor NHR-14 and DNA damage checkpoints (CLK-2, HUS-1, and MRT-2) in nematodes. These findings provide important insights into the exposure risk of PE-NPs on reproduction of environmental organisms.

Size-dependent and sex-specific negative effects of micro- and nano-sized polystyrene particles in the terrestrial invertebrate model Drosophila melanogaster

Microplastic pollution is believed to be one of the most widespread and long-lasting changes on a global scale. Our understanding that microplastics significantly impact terrestrial systems and are a global change stressor continues to grow. In the present study, we investigated the negative effect of long-term (28 days of exposure in food) polystyrene particles of micro (1.0-1.9 µm, 0.4-0.6 µm) and nano (0.04-0.06 µm) scale, in low doses, on the fruit fly - representing a common, globally distributed terrestrial invertebrate, and a model species in many fields. Our observations involved such parameters as ingestion and transfer of particles, survival, reproduction, changes in ultrastructure and tissue and cell responses in midgut epithelium (the place of direct contact with plastic), ovary, and testis in adults, and transgenerational effects in larvae. These observations may indicate possible toxic effects of the tested substances, even in low doses, that can be expected in other taxa, in terrestrial ecosystems. We observed a negative impact of polystyrene particles on the fruit fly survival, midgut, ovary, and testis, involving ultrastructural alterations, such as autophagy and/or ultimately necrosis in the midgut, triggering oxidative stress and activating processes of antioxidative protection. Despite the changes, midgut function and reproduction were not altered - spermatogenesis and oogenesis proceeded normally. The effect was size-dependent - the smaller the polystyrene particles were, the more substantial was the impact they caused. Ultrastructural changes and studied parameters, i.e., generation of ROS (overproduction of which generates oxidative stress), total glutathione concentration (involved in defense against ROS, acting in distinct pathways), and total antioxidant concentration (the oxidative defense system) showed the highest levels after exposure to the smallest nanoparticles, and vice versa. The effect was also sex-dependent, with male flies being more sensitive. Negative effects in males were more substantial and more prominent, even after contact with larger particles, compared to females. The smaller particles (0.4-0.6 µm, 0.04-0.06 µm) were transferred to the ovary and accumulated in the oocytes. In this case, a transgenerational negative effect was detected in larvae. It was characterized by size-dependent alterations, with smaller particles triggering higher levels of ROS and cellular oxidative response. Only the largest particles (1.0-1.9 µm) did not pass into the gonad and did not alter the larvae. These observations together demonstrated that polystyrene particles of micro- and nanoscale, even in a low dose, can induce numerous negative effects on terrestrial invertebrates.

Hermit crabs as model species for investigating the behavioural responses to pollution

Human impacts on the environment affect organisms at all levels of biological organisation and ultimately can change their phenotype. Over time, phenotypic change may arise due to selection but individual phenotypes are also subject to change via genotype × environment interactions. In animals, behaviour is the most flexible aspect of phenotype, and hence the most liable to change across environmental gradients including exposure to pollution. Here we review current knowledge on the impacts of pollution, broadly defined to include the release of substances, energy, and the effects of carbon emissions, on the behaviour of a highly studied group, the globally distributed hermit crabs. We first show how their obligate association with empty gastropod shells underpins their use as model organisms for the study of resource-assessment, contest, and risk-coping behaviours. Intense study of hermit crabs has advanced our understanding of how animals use information, and we discuss the ways in which pollutants can disrupt the cognitive processes involved. We then highlight current studies of hermit crabs, which paint a clear picture of behavioural changes due to multiple pollutants. Impacts on behaviour vary across pollutants and entire suites of behaviours can be influenced by a single pollutant, with the potential for interactive and cascade effects. Hermit crabs offer the opportunity for detailed behavioural analysis, including application of the repeated measures animal-personality framework, and they are highly amenable to experimental manipulations. As such, we show how they now provide a model system for studying the impacts of pollution on behaviour, yielding insights broadly applicable across animal diversity.

Polystyrene microplastics disrupt female reproductive health and fertility via sirt1 modulation in zebrafish (Danio rerio)

Microplastics (MPs) pollution poses an emerging threat to aquatic biota, which could hinder their physiological processes. Recently various evidence has demonstrated the toxic impacts of MPs on cellular and organismal levels, but still, the underlying molecular mechanism behind their toxicity remains ambiguous. The hypothalamic-pituitary-gonadal (HPG) axis regulates the synthesis and release of sex steroid hormones, and SIRT1 plays a vital role in this process. The current study aimed to elucidate the harmful effects of MPs on female reproduction via SIRT1 modulation. Healthy female zebrafish were exposed to different concentrations (50 and 500 µg/L) of polystyrene microplastics (PS-MPs). The results revealed a significant change in the gonadosomatic index (GSI) after exposure to PS-MPs. In addition, the decreased fecundity rate displayed an evident dosage effect, indicating that exposure to PS-MPs causes deleterious effects on fertilization. Furthermore, significantly enhanced levels of reactive oxygen species (ROS) and apoptotic signals through the TUNEL assay were evaluated in different treated groups. Moreover, morphological alterations in the gonads of zebrafish exposed to MPs were also observed through H&E staining. The subsequent change in plasma steroid hormone levels (E2/T ratio) showed an imbalance in hormonal homeostasis. Meanwhile, to follow PS-MPs' effects on the HPG axis via SIRT1 modulation and gene expression related to steroidogenesis, SIRT1/p53 pathway was evaluated through qPCR. The altered transcription levels of genes indicated the plausible interference of PS-MPs on the HPG axis function. Our in-silico molecular docking study proves that PS-MPs efficiently bind and inhibit endocrine receptors and SIRT1. Thus, these findings add to our understanding of the probable molecular mechanisms of reproductive impairment caused by PS-MPs in zebrafish.

Enzyme-immobilized hierarchically porous covalent organic framework biocomposite for catalytic degradation of broad-range emerging pollutants in water

Efficient enzyme immobilization is crucial for the successful commercialization of large-scale enzymatic water treatment. However, issues such as lack of high enzyme loading coupled with enzyme leaching present challenges for the widespread adoption of immobilized enzyme systems. The present study describes the development and bioremediation application of an enzyme biocomposite employing a cationic macrocycle-based covalent organic framework (COF) with hierarchical porosity for the immobilization of horseradish peroxidase (HRP). The intrinsic hierarchical porous features of the azacalix[4]arene-based COF (ACA-COF) allowed for a maximum HRP loading capacity of 0.76 mg/mg COF with low enzyme leaching (<5.0 %). The biocomposite, HRP@ACA-COF, exhibited exceptional thermal stability (∼200 % higher relative activity than the free enzyme), and maintained ∼60 % enzyme activity after five cycles. LCMSMS analyses confirmed that the HRP@ACA-COF system was able to achieve > 99 % degradation of seven diverse types of emerging pollutants (2-mercaptobenzothiazole, paracetamol, caffeic acid, methylparaben, furosemide, sulfamethoxazole, and salicylic acid)in under an hour. The described enzyme-COF system offers promise for efficient wastewater bioremediation applications.

In Silico Study of Enzymatic Degradation of Bioplastic by Microalgae: An Outlook on Microplastic Environmental Impact Assessment, Challenges, and Opportunities

Microplastics are tiny pieces of non-biodegradable plastic that can take thousands of years to break down. As microplastics degrade, they release harmful compounds into the environment, which can be found in the surroundings. The microplastics found in the environment are hard to detect and remove because of their small particle sizes. Microplastics cannot decompose naturally, so they accumulate in the environment and cause pollution. As a result, bioplastics can be produced from a vast array of substrates, including biopolymers, citrus peels, leather, and feather wastes. Blue-green microalgae namely Arthrospira platensis (spirulina) contains enzymes such as laccase and catalase which can be responsible for the degradation of bioplastics. In our study, we performed molecular docking to identify the binding affinities of different enzymes such as laccase and catalase with different substrates, focusing on determining the most suitable substrate for enhancing enzyme activity for degradation of bioplastics. The analysis revealed that veratryl alcohol is the most suitable substrate for laccase, whereas lignin is the more preferred substrate for catalase with the highest binding affinity score of - 5.9 and - 8.1 kcal/mol. Moreover, degradation, challenges, opportunities, and applications of bioplastics in numerous domains such as cosmetics, electronics, agriculture, medical, textiles, and food industries have also been highlighted.

Sources, Degradation, Ingestion and Effects of Microplastics on Humans: A Review

Celluloid, the predecessor to plastic, was synthesized in 1869, and due to technological advancements, plastic products appear to be ubiquitous in daily life. The massive production, rampant usage, and inadequate disposal of plastic products have led to severe environmental pollution. Consequently, reducing the employment of plastic has emerged as a pressing concern for governments globally. This review explores microplastics, including their origins, absorption, and harmful effects on the environment and humans. Several methods exist for breaking down plastics, including thermal, mechanical, light, catalytic, and biological processes. Despite these methods, microplastics (MPs, between 1 and 5 mm in size) continue to be produced during degradation. Acknowledging the significant threat that MPs pose to the environment and human health is imperative. This form of pollution is pervasive in the air and food and infiltrates our bodies through ingestion, inhalation, or skin contact. It is essential to assess the potential hazards that MPs can introduce. There is evidence suggesting that MPs may have negative impacts on different areas of human health. These include the respiratory, gastrointestinal, immune, nervous, and reproductive systems, the liver and organs, the skin, and even the placenta and placental barrier. It is encouraging to see that most of the countries have taken steps to regulate plastic particles. These measures aim to reduce plastic usage, which is essential today. At the same time, this review summarizes the degradation mechanism of plastics, their impact on human health, and plastic reduction policies worldwide. It provides valuable information for future research on MPs and regulatory development.

Review of microplastics in museum specimens: An under-utilized tool to better understand the Plasticene

This study summarises the status of microplastic research in marine and freshwater specimens in natural museum collections around the world. Abundances, distributions, and types of microplastics in the archived collections are discussed. Museum collections can fill knowledge gaps on evolution of microplastic pollution before and during the Plasticene era. The specimens in these studies, ranging from plankton to vertebrates, were collected and archived between 1900 and 2019, and are dominated by specimens from marine ecosystems. All the specimens included in this review were preserved by freezing or in ethanol/formaldehyde except for specimens in one study that were preserved via cryomilling. Microfibers were the most common microplastics in the reviewed studies. We recommend more microplastic studies over a wider taxonomic range of species and across a longer span of years utilizing archival specimen collections around the world in order to establish reference points and develop temporal trends for microplastic pollution of the environment.

Protective Role of Kelulut Honey against Toxicity Effects of Polystyrene Microplastics on Morphology, Hormones, and Sex Steroid Receptor Expression in the Uterus of Rats

BACKGROUND

Microplastics (MPs) are an emerging global pollutant. Previous studies have revealed that chronic exposure to MPs can affect animal and human reproductive health, particularly by impairing the reproductive system's normal functions, which may increase the risk of infertility in both males and females. Kelulut honey (KH), an excellent source of antioxidants, has been used to counteract the disruptive effects of Polystyrene microplastics (PS-MPs) in the rat uterus. Thus, this study aimed to investigate the potential protective effects of Kelulut honey against PS-MPs-induced uterine toxicity in pubertal rats.

METHODS

Prepubertal female Sprague Dawley rats were divided into four groups (n = 8): (i) normal control group (NC: treated with deionized water), MPs-exposed group (M: exposed to PS-MPs at 2.5 mg/kg), (iii) Kelulut honey group (DM: pretreated with 1200 mg/kg of KH 30 minutes before they were administered with PS-MPs at 2.5 mg/kg), and (iv) Kelulut honey control group (DC: only treated with KH at 2.5 mg/kg). The rats were treated orally once daily for six consecutive weeks.

RESULTS

Uterine abnormalities in PS-MPs-exposed rats were significantly improved after concurrent treatment with Kelulut honey. Morphology improvement was observed and luminal epithelial cells seemed thicker with more goblet cells, glandular cells had a more regular and circular shape, stromal cell increased in size, interstitial gaps between stromal cells expanded, and the myometrium layer was thicker. Kelulut honey treatment also effectively normalized the suppressive effect of PS-MPs on the expression and distribution of sex steroid receptors (ERα and ERβ), as well as the level of serum gonadotropin (LH and FSH) and sex steroid (estradiol and progesterone) hormones.

CONCLUSION

Kelulut honey can protect the female reproductive system against the disruptive effects of PS-MPs. The phytochemical properties of Kelulut honey might be responsible for these beneficial benefits. However, future studies are warranted to identify the mechanisms involved.

Mechanisms of microplastics trapping in river sediments: Insights from the Arno river (Tuscany, Italy)

Rivers efficiently convey microplastics to the sea, but during this transfer microplastic can be temporary stored in sediments, where they undergo further fragmentation due to biological and physical processes. Aiming at shedding light on mechanisms governing microplastic sedimentation in rivers, we analyse deposits accumulated in alternate bars of the Arno River (central Italy). Specifically, we considered microplastics associated with floating plant debris, and those trapped in clastic suspended and bedload deposits. The overall concentration of microplastic ranges between 0.44 and 5.68 items per gram, and is comparable with that of some highly-polluted rivers in the world. Fibers are prevalent among the recovered items, and composition is dominated by nylon. Our measurements reveal that microplastics can be easily trapped by floating plant debris, and stored on bar top zones and river banks. Microplastics are also trapped in gravel and sand deposits. Sand incorporates microplastics both when it is transported at the river bottom under tractional conditions and during the waning flood stage, when settling processes contribute to bed aggradation. Gravels do not entraps microplastics when they move on the river bed, but they are extremely efficient in trapping microplastics during recessional flood stages, when water infiltrates between larger clasts, where it drops suspended microplastics. Further studies based on application of principles of fluvial sedimentology will provide crucial insights to understand mechanisms controlling transport and storage of MPs in river sediments.

Caenorhabditis elegans as a Prediction Platform for Nanotechnology-Based Strategies: Insights on Analytical Challenges

Nanotechnology-based strategies have played a pivotal role in innovative products in different technological fields, including medicine, agriculture, and engineering. The redesign of the nanometric scale has improved drug targeting and delivery, diagnosis, water treatment, and analytical methods. Although efficiency brings benefits, toxicity in organisms and the environment is a concern, particularly in light of global climate change and plastic disposal in the environment. Therefore, to measure such effects, alternative models enable the assessment of impacts on both functional properties and toxicity. Caenorhabditis elegans is a nematode model that poses valuable advantages such as transparency, sensibility in responding to exogenous compounds, fast response to perturbations besides the possibility to replicate human disease through transgenics. Herein, we discuss the applications of C. elegans to nanomaterial safety and efficacy evaluations from one health perspective. We also highlight the directions for developing appropriate techniques to safely adopt magnetic and organic nanoparticles, and carbon nanosystems. A description was given of the specifics of targeting and treatment, especially for health purposes. Finally, we discuss C. elegans potential for studying the impacts caused by nanopesticides and nanoplastics as emerging contaminants, pointing out gaps in environmental studies related to toxicity, analytical methods, and future directions.

Caenorhabditis elegans: a model organism in the toxicity assessment of environmental pollutants

The unfavorable effects of environmental pollutants are becoming increasingly evident. In recent years, Caenorhabditis elegans (C. elegans) has been used as a powerful terrestrial model organism for environmental toxicity studies owing to its various advantages, including ease of culture, short lifespan, small size, transparent body, and well-characterized genome. In vivo bioassays and field studies can analyze and evaluate various toxic effects of the toxicants on the model organism, while emerging technologies allow profound insights into molecular disturbances underlying the observed phenotypes. In this review, we discuss the applications of C. elegans as a model organism in environmental toxicity studies and delineate apical assays such as lifespan, growth rate, reproduction, and locomotion, which are widely used in toxicity evaluation. In addition to phenotype assays, a comprehensive understanding of the toxic mode of action and mechanism can be achieved through a highly sensitive multi-omics approach, including the expression levels of genes and endogenous metabolites. Recent studies on environmental toxicity using these approaches have been summarized. This review highlights the practicality and advantages of C. elegans in evaluating the toxicity of environmental pollutants and presents the findings of recent toxicity studies performed using this model organism. Finally, we propose crucial technical considerations to escalate the appropriate use of C. elegans in examining the toxic effects of environmental pollutants.

Drosophila melanogaster as a dynamic in vivo model organism reveals the hidden effects of interactions between microplastic/nanoplastic and heavy metals

Plastic waste in different environments has been constantly transforming into microplastic/nanoplastic (MNPLs). As they may coexist with other contaminants, they may behave as vectors that transport various toxic trace elements, including metals. Because the impact of exposure to such matter on health still remains elusive, the abundant presence of MNPLs has lately become a pressing environmental issue. Researchers have been utilizing Drosophila melanogaster as a dynamic in vivo model in genetic research for some time. The fly has also recently gained wider recognition in toxicology and nanogenotoxicity studies. The use of nanoparticles in numerous medical and consumer products raises serious concern, since many in vitro studies have shown their toxic potential. However, there is rather limited in vivo research into nanomaterial genotoxicity using mice or other mammalians owing to high costs and ethical concerns. In this context, Drosophila, thanks to its genetic tractability, short life span, with its entire life cycle lasting about 10 days, and distinct developmental stages, renders this organism an excellent model in testing toxic effects mediated by MNPLs. This review therefore aims to encourage research entities to employ Drosophila as a model in their nanogenotoxicity experiments focusing on impact of MNPLs at the molecular level.

The gut microbiota, a key to understanding the health implications of micro(nano)plastics and their biodegradation

The effects of plastic debris on the environment and plant, animal, and human health are a global challenge, with micro(nano)plastics (MNPs) being the main focus. MNPs are found so often in the food chain that they are provoking an increase in human intake. They have been detected in most categories of consumed foods, drinking water, and even human feces. Therefore, oral ingestion becomes the main source of exposure to MNPs, and the gastrointestinal tract, primarily the gut, constantly interacts with these small particles. The consequences of human exposure to MNPs remain unclear. However, current in vivo studies and in vitro gastrointestinal tract models have shown that MNPs of several types and sizes impact gut intestinal bacteria, affecting gut homeostasis. The typical microbiome signature of MNP ingestion is often associated with dysbiosis and loss of resilience, leads to frequent pathogen outbreaks, and local and systemic metabolic disorders. Moreover, the small micro- and nano-plastic particles found in animal tissues with accumulated evidence of microbial degradation of plastics/MNPs by bacteria and insect gut microbiota raise the issue of whether human gut bacteria make key contributions to the bio-transformation of ingested MNPs. Here, we discuss these issues and unveil the complex interplay between MNPs and the human gut microbiome. Therefore, the elucidation of the biological consequences of this interaction on both host and microbiota is undoubtedly challenging. It is expected that microbial biotechnology and microbiome research could help decipher the extent to which gut microorganisms diversify and MNP-determinant species, mechanisms, and enzymatic systems, as well as become important to understand our response to MNP exposure and provide background information to inspire future holistic studies.

Microplastic exposure in aquatic invertebrates can cause significant negative effects compared to natural particles - A meta-analysis

Many studies have now reported adverse effects of exposure to microplastics in aquatic organisms. Still, relatively few studies have compared the effects of MPs with those of natural particle controls, which makes it difficult to separate particle effects from chemical effects. In this study, we carry out a meta-analysis of 26 studies to compare the effects of MPs and natural particles on aquatic animals using three different endpoints - growth, reproduction, and mortality. This analysis showed that MPs have the capacity to induce more adverse effects on growth, reproduction, and mortality for some taxonomic groups. However, the effects of exposure to MPs are not consistent across each endpoint or between taxonomic groups. We were not able to clearly discern differing impacts resulting from exposure to specific polymer types or shapes, though more negative effects were associated with polylactic acid and polyethylene, as well as fragments as opposed to beads or fibres. Additionally, meta-regression indicated that larger MP sizes, higher experimental temperatures, and longer exposure periods were all generally associated with more adverse effects. Future studies should continue to make use of negative particle controls to allow for better risk assessment of microplastics and nanoplastics in aquatic ecosystems.

Placental plastics in young women from general population correlate with reduced foetal growth in IUGR pregnancies

Constant exposure to plastics particulates has raised concerns against human health, particularly when it comes to birth outcomes. The present study explores the first appraisal of plastic particles in fresh human placenta and its association with foetal growth in neonates. Specifically, 43 pregnant women from general population were selected and their placentas were analyzed by digital microscopy and Raman microspectroscopy for microplastics (MPs <5 mm). We used regression analysis to estimate associations between MPs count in placenta and neonatal anthropometric measurements. MPs were found in all (13 out of 13) intrauterine growth restriction (IUGR) pregnancies and their average abundance ranged from 2 to 38 particles per placenta, but were less than limit of detection (LOD) in normal pregnancies except three out of 30 subjects. This study is one of very few that detected MPs in human placenta in which particles <10 μm were the most abundant in both IUGR and normal pregnancies, accounting for up to 64%. Fragments clearly prevailed at normal pregnancies and fragments together with fibers predominated at IUGR placentas. Despite four different polymers forming the MPs being identified, the majority of MPs comprised of PE (polyethylene) and PS (polystyrene). Inverse associations between MPs exposure and birth outcomes were observed in terms of birth weight (r = - 0.82, p < 0.001), length (r = - 0.56, p < 0.001), head circumference (r = - 0.50, p = 0.001), and 1-min Apgar score (r = - 0.75, p < 0.001) among those with IUGR, compared to those that were nominated as normal pregnancies. While it seems plastic particles may affect placental-foetal interrelationship, the pattern of associations between their content in placenta and birth outcomes, however, shows evidence of a nonlinear or nonmonotonic dose response possibly through perturbation of gas and nutrients exchange which is worth future investigation.

Interactions of Ingested Polystyrene Microplastics with Heavy Metals (Cadmium or Silver) as Environmental Pollutants: A Comprehensive In Vivo Study Using Drosophila melanogaster

Living organisms are now constantly exposed to microplastics and nanoplastics (MNPLs), and besides their toxic potential, they can also act as carriers of various hazardous elements such as heavy metals. Therefore, this study explored possible interactions between polystyrene microplastics (PSMPLs) and two metal pollutants: cadmium chloride (CdCl2) and silver nitrate (AgNO3). To better understand the extent of biological effects caused by different sizes of PSMPLs, we conducted in vivo experiments with five doses (from 0.01 to 10 mM) that contained polystyrene particles measuring 4, 10, and 20 µm in size on Drosophila larvae. Additional experiments were performed by exposing larvae to two individual metals, CdCl2 (0.5 mM) and AgNO3 (0.5 mM), as well as combined exposure to PSMPLs (0.01 and 10 mM) and these metals, in an attempt to gain new insight into health risks of such co-exposure. Using transmission electron microscopy imaging, we managed to visualize the biodistribution of ingested PSMPLs throughout the fly's body, observing the interactions of such plastics with Drosophila intestinal lumen, cellular uptake by gut enterocytes, the passage of plastic particles through the intestinal barrier to leak into the hemolymph, and cellular uptake by hemocytes. Observations detected size and shape changes in the ingested PSMPLs. Egg-to-adult viability screening revealed no significant toxicity upon exposure to individual doses of tested materials; however, the combined exposure to plastic and metal particles induced aggravated genotoxic effects, including intestinal damage, genetic damage, and intracellular oxidative stress (ROS generation), with smaller sized plastic particles + metals (cadmium and silver) causing greater damage.

Nanoplastics cause transgenerational toxicity through inhibiting germline microRNA mir-38 in C. elegans

Nanoplastic exposure potentially caused the induction of transgenerational toxicity. Nevertheless, the molecular basis for nanoplastic exposure-induced transgenerational toxicity remains largely unclear. Using Caenorhabditis elegans as an animal model, we examined the role of germline microRNA (miRNA) mir-38 in regulating the transgenerational toxicity of polystyrene nanoparticles (PS-NPs). After the exposure, 1-100 μg/L PS-NP decreased expression of germline mir-38. Meanwhile, germline mir-38 overexpression conferred a resistance to transgenerational PS-NP toxicity, which suggested that the decrease in germline mir-38 mediated the induction of transgenerational PS-NP toxicity. In the germline, mir-38 regulated transgenerational PS-NP toxicity by inhibiting activity of downstream targets (NDK-1, NHL-2, and WRT-3). Among these three downstream targets, germline NDK-1 further controlled transgenerational PS-NP toxicity by suppressing the function of KSR-1/2, two kinase suppressors of Ras. Therefore, in the germline, the decrease in mir-38 mediated induction of transgenerational PS-NP toxicity by at least inhibiting signaling cascade of NDK-1-KSR-1/2 in nematodes. The findings in this study are helpful for providing relevantly molecular endpoints to assess potential transgenerational toxicity of nanoplastics.

Macro- and Microplastics in the Antarctic Environment: Ongoing Assessment and Perspectives

The number of scientists and tourists visiting Antarctica is on the rise and, despite the management framework for environmental protection, some coastal areas, particularly in the Antarctic Peninsula region, are affected by plastic contamination. The few data available on the occurrence of microplastics (<5 mm) are difficult to compare, due to the different methodologies used in monitoring studies. However, indications are emerging to guide future research and to implement environmental protocols. In the surface and subsurface waters of the Southern Ocean, plastic debris >300 µm appears to be scarce and far less abundant than paint chips released from research vessels. Yet, near some coastal scientific stations, the fragmentation and degradation of larger plastic items, as well as microbeads and microfibers released into wastewater from personal care products and laundry, could potentially affect marine organisms. Some studies indicate that, through long-range atmospheric transport, plastic fibers produced on other continents can be deposited in Antarctica. Drifting plastic debris can also cross the Polar Front, with the potential to carry alien fouling organisms into the Southern Ocean. Sea ice dynamics appear to favor the uptake of microplastics by ice algae and Antarctic krill, the key species in the Antarctic marine food web. Euphausia superba apparently has the ability to fragment and expel ingested plastic particles at the nanoscale. However, most Antarctic organisms are endemic species, with unique ecophysiological adaptations to extreme environmental conditions and are likely highly sensitive to cumulative stresses caused by climate change, microplastics and other anthropogenic disturbances. Although there is limited evidence to date that micro- and nanoplastics have direct biological effects, our review aims at raising awareness of the problem and, in order to assess the real potential impact of microplastics in Antarctica, underlines the urgency to fill the methodological gaps for their detection in all environmental matrices, and to equip scientific stations and ships with adequate wastewater treatment plants to reduce the release of microfibers.