Chronic toxic effects of polystyrene microplastics on reproductive parameters of male rats

The hidden threat: Unraveling the impact of microplastics on reproductive health

Microplastics, with intricate physical and chemical characteristics, infiltrate the food chain and extensively impact ecosystems. Despite acknowledging the link between environmental pollution and declining fertility, the specific mechanisms affecting reproductive health remain to be elucidated. This review emphasizes the global correlation between microplastics and subfertility, focusing on entry pathways and impacts on ecosystems. Research suggests that microplastics disrupt the neuroendocrine system, influencing sex hormone synthesis through the hypothalamic-pituitary-gonadal (HPG) axis. In the reproductive system, microplastics interfere with the blood-testis barrier, impairing spermatogenesis in males, and causing placental dysfunction, ovarian atrophy, endometrial hyperplasia, and fibrosis in females. Moreover, microplastics potentially affect offspring's lipid metabolism and reproductive functions. However, complex microplastic compositions and detection method limitations impede research progress. Mitigation strategies for reproductive effects, combined with addressing microplastic pollution through sustainable practices, are imperative. This review underscores the urgency of global initiatives and collaborative research to safeguard reproductive health amid escalating microplastic contamination.

Convenient determination of polystyrene microplastics in soils by gel permeation chromatography-ultraviolet detection analysis

Microplastics (MPs), especially polystyrene microplastics (PS-MPs), have emerged a new worldwide pollutant, prompting significant public concern regarding their detection in environmental media. Analysis of PS-MPs in soil remains as a challenging task for analysts due to the highly intricate matrices. This work presents a practical approach for detecting PS-MPs in soil, which involves dilute HCl-assisted extraction and gel permeation chromatography- ultraviolet detection (GPC-UV) analysis. The presence of MPs in soil was confirmed through the use of a scanning electron microscope in conjunction with energy dispersive spectroscopy investigation. PS-MPs was isolated from soil, by agitating it with a diluted HCl solution, filtering the resulting liquid, and dissolving the residue on the filter with THF. The extractant was subsequently determined by GPC-UV. The introduction of a small amount of HCl into the extraction system was found to greatly expedite the settling of soil in water and enhance the efficacy of extracting PS-MPs in about 30 min. The linear range of PS-MPs was from 1.0 to 100 μg/mL with R2 > 0.999. Good reproducibility was obtained with the intra-day relative standard deviation (RSD, n = 3) of 1.36 % and the inter-day RSD (n = 3) of 4.78 %. The concentration of PS-MPs in soil samples were N.D. - 2.33 μg/g, and the good recoveries were 76.7-100.3 %. The corresponding AFGEEprer score was calculated to be 0.59, indicating the concept of green analytical chemistry for the pretreatment method. These results indicated that this method has a powerful potential for the accurate and rapid determination of PS-MPs in soil.

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.

Adverse effects and potential mechanisms of polystyrene microplastics (PS-MPs) on the blood-testis barrier

Microplastics (MPs) are defined as plastic particles or fragments with a diameter of less than 5 mm. These particles have been identified as causing male reproductive toxicity, although the precise mechanism behind this association is yet to be fully understood. Recent research has found that exposure to polystyrene microplastics (PS-MPs) can disrupt spermatogenesis by impacting the integrity of the blood-testis barrier (BTB), a formidable barrier within mammalian blood tissues. The BTB safeguards germ cells from harmful substances and infiltration by immune cells. However, the disruption of the BTB leads to the entry of environmental pollutants and immune cells into the seminiferous tubules, resulting in adverse reproductive effects. Additionally, PS-MPs induce reproductive damage by generating oxidative stress, inflammation, autophagy, and alterations in the composition of intestinal flora. Despite these findings, the precise mechanism by which PS-MPs disrupt the BTB remains inconclusive, necessitating further investigation into the underlying processes. This review aims to enhance our understanding of the pernicious effects of PS-MP exposure on the BTB and explore potential mechanisms to offer novel perspectives on BTB damage caused by PS-MPs.

A critical review on male-female reproductive and developmental toxicity induced by micro-plastics and nano-plastics through different signaling pathways

It is widely accepted that humans are constantly exposed to micro-plastics and nano-plastics through various routes, including inhalation of airborne particles, exposure to dust, and consumption of food and water. It is estimated that humans may consume thousand to millions of micro-plastic particles, equating to several milligrams per day. Prolonged exposure to micro-plastics and nano-plastics has been linked to negative effects on different living organisms, including neurotoxicity, gastrointestinal toxicity, nephrotoxicity, and hepatotoxicity, and developmental toxicities. The main purpose of this review is to explore the effect of micro-plastics and nano-plastics on the male and female reproductive system, as well as their offspring, and the associated mechanism implicated in the reproductive and developmental toxicities. Micro-plastics and nano-plastics have been shown to exert negative effects on the reproductive system of both male and female mammals and aquatic animals, including developmental impacts on gonads, gametes, embryo, and their subsequent generation. In addition, micro-plastics and nano-plastics impact the hypothalamic-pituitary axes, leading to oxidative stress, reproductive toxicity, neurotoxicity, cytotoxicity, developmental abnormalities, poor sperm quality, diminishes ovarian ovulation and immune toxicity. This study discusses the so many different signaling pathways associated in the male and female reproductive and developmental toxicity induced by micro-plastics and nano-plastics.

The possible impacts of nano and microplastics on human health: lessons from experimental models across multiple organs

The widespread production and use of plastics have resulted in accumulation of plastic debris in the environment, gradually breaking down into smaller particles over time. Nano-plastics (NPs) and microplastics (MPs), defined as particles smaller than 100 nanometers and 5 millimeters, respectively, raise concerns due to their ability to enter the human body through various pathways including ingestion, inhalation, and skin contact. Various investigators demonstrated that these particles may produce physical and chemical damage to human cells, tissues, and organs, disrupting cellular processes, triggering inflammation and oxidative stress, and impacting hormone and neurotransmitter balance. In addition, micro- and nano-plastics (MNPLs) may carry toxic chemicals and pathogens, exacerbating adverse effects on human health. The magnitude and nature of these effects are not yet fully understood, requiring further research for a comprehensive risk assessment. Nevertheless, evidence available suggests that accumulation of these particles in the environment and potential human uptake are causes for concern. Urgent measures to reduce plastic pollution and limit human exposure to MNPLs are necessary to safeguard human health and the environment. In this review, current knowledge regarding the influence of MNPLs on human health is summarized, including toxicity mechanisms, exposure pathways, and health outcomes across multiple organs. The critical need for additional research is also emphasized to comprehensively assess potential risks posed by degradation of MNPLs on human health and inform strategies for addressing this emerging environmental health challenge. Finally, new research directions are proposed including evaluation of gene regulation associated with MNPLs exposure.

Combined effects of polystyrene nanoplastics and lipopolysaccharide on testosterone biosynthesis and inflammation in mouse testis

Microplastics (MPs)/nanoplastics (NPs), as a source and vector of pathogenic bacteria, are widely distributed in the natural environments. Here, we investigated the combined effects of polystyrene NPs (PS-NPs) and lipopolysaccharides (LPS) on testicular function in mice for the first time. 24 male mice were randomly assigned into 4 groups, control, PS-NPs, LPS, and PS-NPs + LPS, respectively. Histological alterations of the testes were observed in mice exposed to PS-NPs, LPS or PS-NPs + LPS. Total sperm count, the levels of testosterone in plasma and testes, the expression levels of steroidogenic acute regulatory (StAR) decreased more remarkable in testes of mice treated with PS-NPs and LPS than the treatment with LPS or PS-NPs alone. Compared with PS-NPs treatment, LPS treatment induced more sever inflammatory response in testes of mice. Moreover, PS-NPs combined with LPS treatment increased the expression of these inflammatory factors more significantly than LPS treatment alone. In addition, PS-NPs or LPS treatment induced oxidative stress in testes of mice, but their combined effect is not significantly different from LPS treatment alone. These results suggest that PS-NPs exacerbate LPS-induced testicular dysfunction. Our results provide new evidence for the threats to male reproductive function induced by both NPs and bacterial infection in human health.

Microplastics reach the brain and interfere with honey bee cognition

Scientific research on the impact of microplastics (MPs) in terrestrial systems is still emerging, but it has confirmed adverse health effects in organisms exposed to plastics. Although recent studies have shown the toxicological effects of individual MPs polymers on honey bees, the effects of different polymer combinations on cognitive and behavioural performance remain unknown. To fill this knowledge gap, we investigated the effects of oral exposure to spherical MPs on cognitive performance and brain accumulation in the honey bee Apis mellifera. We evaluated the acute toxicity, after a two-day exposure, of polystyrene (PS - 4.8-5.8 μm) and plexiglass (Poly(methyl methacrylate), or PMMA - 1-40 μm) MPs, and a combination of the two (MIX), at two environmentally relevant and one higher concentration (0.5, 5 and 50 mg L-1) and analysed their effects on sucrose responsiveness and appetitive olfactory learning and memory. We also used fluorescent thermoset amino formaldehyde MPs (1-5 μm) to explore whether microspheres of this diameter could penetrate the insect blood-brain barrier (BBB), using Two-Photon Fluorescence Microscopy (TPFM) in combination with an optimized version of the DISCO clearing technique. The results showed that PS reduced sucrose responsiveness, while PMMA had no significant effect; however, the combination had a marked negative effect on sucrose responsiveness. PMMA, PS, and MIX impaired bee learning and memory in bees, with PS showing the most severe effects. 3D brain imaging analysis using TFPM showed that 1-5 μm MPs penetrated and accumulated in the brain after only three days of oral exposure. These results raise concerns about the potential mechanical, cellular, and biochemical damage that MPs may cause to the central nervous system.

Pharmacotherapeutic potential of ginkgetin against polystyrene microplastics-instigated testicular toxicity in rats: A biochemical, spermatological, and histopathological assessment

Polystyrene microplastics (PSMPs) have emerged as a ubiquitous environmental toxicant that affects different organs including testes. Ginkgetin (GNG) is a biflavonoid that shows antioxidant properties. The current research was undertaken to evaluate the ameliorative potential of GNG against PSMPs-instigated testicular damages. Forty-eight albino rats (male) were randomly divided into 4 equal groups: control, PSMPs-treated group (0.01 mgkg-1), GNG + PSMPs-exposed group (25 mgkg-1 + 0.01 mgkg-1), and only GNG-supplemented group (25 mgkg-1). After 56 days of treatment, it was revealed that PSMPs significantly reduced the activity of glutathione peroxidase (GPx), catalase (CAT), superoxide dismutase (SOD), and glutathione reductase (GSR), while concurrently augmented the levels of lipid peroxidation marker, i.e., malondialdehyde (MDA) along with reactive oxygen species (ROS). Rats administered with PSMPs showed a significant reduction in the spermatogenic indices (sperm count, viability, and motility), HOS coiled tail sperm along with increased sperm structural deformities, i.e., tail, head, and mid-piece. Additionally, PSMPs exposure decreased the levels of testosterone, luteinizing (LH), and follicle-stimulating hormones (FSH). Besides, administration of PSMPs reduced the steroidogenic enzymes (13β-HSD, StAR, and 17β-HSD) and Bcl-2 expression, while augmented the caspase-3 and Bax expression. PSMPs also elevated the levels of inflammatory markers (IL-6, IL-1β, TNF-α, and NF-κB) and activity of COX-2 in the testes. Furthermore, PSMPs treatment induced various histopathological damages in the testes of rats. Therefore, findings of the current study suggested that GNG effectively mitigated the PSMPs-induced testicular toxicity owing to its chemoprotective potential possibly through its anti-inflammatory, antioxidant, anti-apoptotic, and androgenic properties.

Growth, physiological parameters and DNA methylation in Spirodela polyrhiza (L.) Schleid exposed to PET micro-nanoplastic contaminated waters

The effects of polyethylene terephthalate micro-nanoplastics (PET-MNPs) were tested on the model freshwater species Spirodela polyrhiza (L.) Schleid., with focus on possible particle-induced epigenetic effects (i.e. alteration of DNA methylation status). MNPs (size ∼ 200-300 nm) were produced as water dispersions from PET bottles through repeated cycles of homogenization and used to prepare N-medium at two environmentally relevant concentrations (∼0.05 g L-1 and ∼0.1 g L-1 of MNPs). After 10 days of exposure, a reduction in fresh and dry weight was observed in treated plants, even if the average specific growth rate for both frond number and area was not altered. Impaired growth was coupled with a MNP-induced decrease of chlorophyll fluorescence parameters (i.e. ΨETo and Piabs, indicators of photochemical efficiency) and starch concentration, as well as with alterations in plant ionomic profile and oxidative status. The methylation-sensitive amplification polymorphism (MSAP) technique was used to assess possible changes in DNA methylation levels induced by plastic particles. The analysis showed unusual hypermethylation in 5'-CCGG sites that could be implicated in DNA protection from dangerous agents (i.e. reactive oxygen species) or in the formation of new epialleles. This work represents the first evidence of MNP-induced epigenetic modifications in the plant world.

Do functional traits and biochemical biomarkers of the nematode Oncholaimus campylocercoides De Coninck and Schuurmans Stekhoven, 1933 affected by fluoranthene and polystyrene microplastics? Results from a microcosm bioassay and molecular modeling

The current experiment measured the multifaceted effects of polystyrene and fluoranthene, acting alone or in a mixture, on the meiobenthic nematode species Oncholaimus campylocercoides. This Oncholaimid was first experimentally selected from an entire nematode assemblage taken from the Jeddah coasts (Saudi Arabia). Several discernible changes were found in morphometry and functional traits after exposure to single and combined treatments. An increase in the activity of the biochemical biomarkers catalase and glutathione S-transferase was also observed following the exposure of males and gravid females of O. campylocercoides to 37.5 ng fluoranthene·g-1 dry weight (DW) and 62.5 mg polystyrene·kg-1 DW paralleled by a higher vulnerability of females. Moreover, the reproduction and feeding of this species were impaired, starting from 37.5 ng fluoranthene·g-1 and 62.5 mg polystyrene·kg-1, respectively. These results have been confirmed by good binding affinities and molecular interactions of fluoranthene and polystyrene with both GLD-3 and SDP receptors.

The multifaceted effects of fluoranthene and polystyrene on the taxonomic composition and associated functional traits of marine meiofauna, by using single and mixture applications

The current experiment measured the multifaceted effects of polystyrene and fluoranthene, acting alone or in a mixture on marine meiofauna, but with a special focus on nematodes' morphological and functional traits. The results showed changes in the abundances for all tested concentrations of both compounds. The nematode communities exposed to the highest concentrations of fluoranthene (30 ng.g-1 Dry Weight (DW)) and polystyrene (100 mg.kg-1 DW) alone or in a mixture, were significantly less diverse compared to control and were associated with significant changes in the percentage of taxonomic composition and feeding-guilds. The most sensitive taxa to fluoranthene comprised epistratum feeders, whereas the nematodes mostly affected by polystyrene were omnivores-carnivores. A new functional tool, the Index of Sensitivity (IOS), proved to be reliable in depicting the changes that occurred in the taxonomic and functional features of the nematofauna.

Effects of Micro(nano)plastics on the reproductive system: A review

Microplastics (100nm-5 mm) and nanoplastics (1-100 nm) are collectively referred to as micro(nano)plastics (MNPs), which are refractory to degradation, easy to migration, small in size, strong in adsorption, and can widely present in human living environment. A number of studies have confirmed that MNPs can be exposed to the human body through a variety of routes, and can penetrate various barriers to enter the reproductive system, suggesting that MNPs may pose potential harm to human reproductive health. Current studies most were limited to phenotypic studies and their subjects were basically lower marine organisms and mammals. Therefore, in order to provide theoretical base for further exploring the effects of MNPs on the human reproductive system, this paper searched the relevant literature at home and abroad, mainly analyzed rodent experiments, and concluded that the main exposure routes of MNPs are dietary intake, air inhalation, skin contact and medical plastics. After entering the reproductive system, MNPs produce reproductive toxicity mainly through oxidative stress, inflammation, metabolic disorders, cytotoxicity and other mechanisms. More work is required to comprehensively identify the exposure routes, improve the detection methods to evaluate the effective exposure and deeply study the specific mechanisms of toxic effects, withing the aim of conducting relevant studies at the population level in the next step.

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.

Microplastics as an emerging menace to environment: Insights into their uptake, prevalence, fate, and sustainable solutions

The inflated demand for plastic products has led to tremendous rise in plastic debris in different environmental matrices, thereby resulting in plastic pollution. This affects plants, animals, and even humans, as microplastics can enter the food chain and cause several health implications. Microplastics are the small plastic particles (size below 5 mm) that are largely debated nowadays owing to their environmental risk assessment. Their potential to interact with other toxic contaminants, their tendency to be ingested or taken up by living organisms and their longevity is a serious threat to our environment. However, despite wealth of recent information, still there is a gap, particularly in eco-toxicology studies, fate, prevalence and feasible solutions to cope up with the menace of microplastics pollution. This review unravels the environmental fate and behaviour of microplastics as well as their global distribution in the marine and terrestrial environment. Furthermore, we aim to contribute to the international debate on the microplastics global paradigm. We briefly suggest sustainable solutions and recommendations to achieve future research goals on microplastics. Our review reveals some of the newest biological (green algae and modified sponges) and physical (nano-particles and membrane treatment) remediation solutions to eradicate microplastics from different types of environment. This review presents a critical evaluation of the state of knowledge of micro-plastics and suggested some recommendations which can help in identifying some important key questions for future research.

Combined effect of polystyrene microplastics and cadmium on rat blood-testis barrier integrity and sperm quality

The harmful effects of microplastics and Cd on the testicular activity of sexually mature rats are here documented. Oral treatment with both substances caused testicular impairment that was evidenced by histological and biomolecular alterations, such as MP accumulation in the seminiferous epithelium, imbalance of oxidative status, and reduced sperm quality. Importantly, the cytoarchitecture of the blood-testis barrier was compromised, as revealed by the down-regulation of protein levels of structural occludin, Van Gogh-like protein 2, and connexin 43 and activation of regulative kinases proto-oncogene tyrosine-protein kinase and focal adhesion kinase. Interestingly, for the first time, MPs are reported to activate the autophagy pathway in germ cells, to reduce damaged organelles and molecules, probably in an attempt to avoid apoptosis. Surprisingly, the results obtained with the simultaneous Cd + MPs treatment showed more harmful effects than those produced by MPs alone but less severe than with Cd alone. This might be due to the different ways of administration to rats (oral gavage for MPs and in drinking water for Cd), which might favor the adsorption, in the gastrointestinal tract, of Cd by MPs, which, by exploiting the Trojan horse effect, reduces the bioavailability of Cd.

The simultaneous administration of microplastics and cadmium alters rat testicular activity and changes the expression of PTMA, DAAM1 and PREP

This paper confirms the damaging effects produced by MP and Cd on testicular activity in the rat. Oral treatment with both chemicals resulted in testicular damage, documented by biomolecular and histological alterations, particularly by impaired morphometric parameters, increased apoptosis, reduced testosterone synthesis, and downregulation of the steroidogenic enzyme 3β-HSD. We also demonstrated, for the first time, that both MP and Cd can affect the protein level of PTMA, a small peptide that regulates germ cell proliferation and differentiation. Interestingly, the cytoarchitecture of testicular cells was also altered by the treatments, as evidenced by the impaired expression and localization of DAAM1 and PREP, two proteins involved in actin- and microtubule-associated processes, respectively, during germ cells differentiation into spermatozoa, impairing normal spermatogenesis. Finally, we showed that the effect of simultaneous treatment with MP and Cd were more severe than those produced by MP alone and less harmful than those of Cd alone. This could be due to the different ways of exposure of the two substances to rats (in drinking water for Cd and in oral gavage for MP), since being the first contact in the animals’ gastrointestinal tract, MP can adsorb Cd, reducing its bioavailability through the Trojan-horse effect.

Developmental and reproductive toxic effects of exposure to microplastics: A review of associated signaling pathways

Microplastics (MPs), small pieces of plastic (∼5 mm), are released into the environment not only as a result of the decomposition of large-sized plastics but also from day-to-day use of plastic products. Chronic exposure to MPs has been attributed to harmful effects on aquatic organisms and rodents. Effects include gastrointestinal toxicity, hepatotoxicity, neurotoxicity, and reproductive and developmental toxicities. Exposure to MPs may also potentially affect human health. Herein, we reviewed the impact of MPs on male and female reproductive systems and the associated mechanisms involved in the reproductive and developmental toxicities of MPs. We performed a literature search in Google Scholar and PubMed using the following keywords: MPs and reproductive toxicity; MPs and developmental studies; MPs and infertility; MPs and aquatics; and MPs and rodents. Evidence of MPs accumulation has been reported in many organs of humans and experimental models. The harmful effects of MPs have been manifested in male and female reproductive systems of mammalian and aquatic animals, including developmental effects on gametes, embryos, and their offspring. This review describes various signaling pathways involved in MPs-associated male and female reproductive and developmental toxicities.