Chronic exposure to polystyrene microplastics induced male reproductive toxicity and decreased testosterone levels via the LH-mediated LHR/cAMP/PKA/StAR pathway

Lactating exposure to microplastics at the dose of infants ingested during artificial feeding induced reproductive toxicity in female mice and their offspring

Microplastics (MPs) pollution poses a global environmental challenge with significant concerns regarding its potential impact on human health. Toxicological investigations have revealed multi-system impairments caused by MPs in various organisms. However, the specific reproductive hazards in human contexts remain elusive, and understanding the transgenerational reproductive toxicity of MPs remains limited. This study delves into the reproductive toxicity resulting from lactational exposure to polystyrene MPs (PS-MPs) in female mice, extending the inquiry to assess the reproductive effects on their offspring bred by rigorous natural mating. The MPs dosage corresponds to the detected concentration in infant formula prepared using plastic bottles. By systematically evaluating the reproductive phenotypes of F0 female mice from birth to adulthood, we found that female mice exposed to PS-MPs exhibited delayed puberty, disturbed estrous cyclicity, diminished fertility, elevated testosterone, abnormal follicle development, disrupted ovarian steroidogenesis, and ovarian inflammation. Importantly, the observed inheritable reproductive toxicity manifested with gender specificity, showcasing more pronounced abnormalities in male offspring. Specifically, reproductive disorders did not manifest in female offspring; however, a significant decrease in sperm count and viability was observed in PS-MPs-exposed F1 males. Testicular transcriptomics analysis of F1 males significantly enriched pathways associated with reproductive system development and epigenetic modification, such as male germ cell proliferation, DNA methylation, and histone modification. In summary, real-life exposure to PS-MPs impaired the reproductive function of female mice and threateningly disrupted the spermatogenesis of their F1 male offspring, which raises serious concerns about inter- and trans-generational reproductive toxicities of MPs in mammals. These findings underscore the potential threats of MPs to human reproductive health, emphasizing the need for continued vigilance and research in this critical area.

Polystyrene microplastics trigger testosterone decline via GPX1

As an emerging environmental endocrine disruptor, polystyrene microplastics (PS-MPs) are considered to have the anti-androgenic feature and impair male reproductive function. To explore the adverse effects of PS-MPs on testosterone synthesis and male reproduction and further elucidate underlying mechanisms, BALB/c mice and Leydig cells were employed in the present work. The results indicated that 50 μm PS-MPs accumulated in mouse testes and were internalized into the cytoplasm. This not only damaged the testicular histomorphology and ultrastructure, but also reduced the viability of Leydig cells and the serum level of GnRH, FSH, LH, and testosterone. After PS-MPs exposure, the ubiquitination degradation and miR-425-3p-targeted modulation synergistically contributed to the suppression of GPX1, which induced oxidative stress and subsequently activated the PERK-EIF2α-ATF4-CHOP pathway of endoplasmic reticulum (ER) stress. The transcription factor CHOP positively regulated the expression of SRD5A2 by directly binding to its promoter region, thereby accelerating testosterone metabolism and ultimately lowing testosterone levels. Besides, PS-MPs compromised testosterone homeostasis via interfering with the hypothalamic-pituitary-testis (HPT) axis. Taken together, PS-MPs possess an anti-androgenic characteristic and exert male reproductive damage effects. The antioxidant enzyme GPX1 plays a crucial role in the PS-MPs-mediated testosterone decline.

Chronic exposure to polystyrene microplastics induced LHR reduction and decreased testosterone levels through NF-κB pathway

The extensive utilization of plastic products in recent years has resulted in a significant contamination of microplastics (MPs). The ingestion of MPs by aquatic and terrestrial organisms facilitates their transmission to mammals through the food chain. Therefore, the toxicity of MPs has attracted widespread attention from researchers. Previous studies have shown a connection between being exposed to polystyrene MPs (PS-MPs) and issues with male reproductive function. Testosterone, a hormone essential for male reproductive function, is produced and secreted by specialized cells known as Leydig cells, which found in the testicular interstitium. In our prior research, we confirmed that exposure to PS-MPs caused a reduction in testosterone levels by interfering with the LH-mediated LHR/cAMP/PKA/StAR pathway, with LHR being pivotal in this mechanism. However, the molecular mechanism underlying PS-MPs-induced reduction of LHR remains unclear. In this study, mice were respectively given drinking water containing 1000 μg/L PS-MPs characterized by diameters of 0.5 μm, 4 μm, and 10 μm for a period of 180 days. Our findings indicated that exposure to PS-MPs resulted in the proliferation of macrophages as well as their polarization towards the M1 phenotype. Additionally, the presence of PS-MPs triggered the release of tumor necrosis factor alpha (TNF-α) from macrophages, thereby activating nuclear factor-κB (NF-κB) signaling pathway within Leydig cells. The translocation of NF-κB into nucleus facilitated its binding to the promoter region of LHR, which consequently led to the repression of LHR transcription. This transcriptional inhibition resulted in a subsequent suppression of testosterone synthesis and secretion. Overall, this study elucidates a theoretical basis for explaining the interference of PS-MPs on the testosterone synthesis and secretion in Leydig cells from the perspective of the interaction between cells in the testicular interstitium.

Rotenone-induced cell apoptosis via endoplasmic reticulum stress and PERK-eIF2α-CHOP signalling pathways in TM3 cells

Rotenone (ROT), a widely used natural pesticide, has an uncertain effect on reproductive toxicity. In this study, we used 20 mice distributed randomly into four groups, with each group receiving ROT doses of 0, 2, 4, and 8 mg/kg/day for 28 days. The results demonstrated that ROT induced significant testicular damage, including impaired spermatogenesis, inhibition of testosterone synthesis, and apoptosis of Leydig cells. Additionally, ROT disrupted the normal ultrastructure of the endoplasmic reticulum (ER) in testicular tissue, leading to ER stress in Leydig cells. To further explore whether ROT-induced apoptosis in Leydig cells is related to ER stress, the mouse Leydig cell line (TM3 cells) was treated with ROT at 0, 250, 500, and 1000 nM. ROT inhibited TM3 cell viability, induced cytotoxicity, and reduced testosterone content in the culture supernatants. Furthermore, ROT treatment triggered apoptosis in TM3 cells by activating ER stress and the PERK-eIF2α-CHOP signalling pathway. Pre-treatment of TM3 cells exposed to ROT with the ER stress inhibitor 4-phenylbutyric acid (4-PBA) alleviated these effects, decreasing apoptosis and preserving testosterone levels. Further intervention with the PERK inhibitor GSK2606414 reduced ROT-induced apoptosis and testosterone reduction by inhibiting PERK activity. In summary, ROT-induced male reproductive toxicity is specifically driven by apoptosis, with the PERK-eIF2α-CHOP signalling pathway activated by ER stress playing a crucial role in the apoptosis of Leydig cells triggered by ROT.

Long-term nanoplastics exposure contributes to impaired steroidogenesis by disrupting the hypothalamic-testis axis: Evidence from integrated transcriptome and metabolome analysis

Cumulative evidence suggested that nanoplastics (NPs) cause male toxicity, but the mechanisms of which are still misty. Steroidogenesis is a key biological event that responsible for maintaining reproductive health. However, whether dysregulated steroidogenesis is involved in NPs-induced impaired male reproductive function and the underlying mechanism remains unclear. In our study, Balb/c mice were continuously exposed to pristine-NPs or NH2-NPs for 12 weeks, spanning the puberty and adult stage. Upon the long-term NPs treatment, the hypothalamus and testis were subjected to transcriptome and metabolome analysis. And the results demonstrated that both primitive-NPs and NH2-NPs resulted in impaired spermatogenesis and steroidogenesis, as evidenced by a significant reduction in sperm quality, testosterone, FSH, and LH. The expression of genes involved in hypothalamic-pituitary-testis (HPT) axis, such as Kiss-1 and Cyp17a1 that encoded the key steroid hormone synthetase, was also diminished. Furthermore, the phosphatidylcholine and pantothenic acid that mainly enriched in glycerophospholipid metabolism were significantly reduced in the testis. Comprehensive analysis of the transcriptome and metabolome indicated that down-regulated Cyp17a1 was associated with decreased metabolites phosphatidylcholine and pantothenic acid. Overall, we speculate that the disturbed HPT axis induced by long-term NPs contributes to disordered glycerophospholipid metabolism and subsequently impaired steroidogenesis. Our findings deepen the understanding of the action of the mechanism responsible for NPs-induced male reproductive toxicology.

Biodistribution of synthesized polyethylene terephthalate fibers in adult zebrafish, their sex hormone disruption effect, and mitigation using natural organic matter

Although polyethylene terephthalate (PET) fibers are a representative form of plastic pollutants, studies on their toxicity are currently limited compared to other plastic types. Moreover, the effect of natural organic matter (NOM) on their toxicity has not been investigated. In this study, female and male adult zebrafish were exposed to synthesized PET fibers at concentrations of 0.1, 1, 10, and 100 mg/L in the presence and absence of 10 mg/L of NOM for 10 d. Bioaccumulation of PET fibers in zebrafish intestine, liver, and gills was identified and expression levels of reactive oxygen species (ROS) generation, sex hormones, and oxidative stress and sex hormone-related genes were measured. In addition, the developmental stages of gonadal cells were examined through histological analysis. We found that PET fibers bioaccumulated in the intestine and liver of zebrafish. ROS generation significantly increased at 100 mg/L of PET fibers, the expression of oxidative stress-related genes decreased in female and increased in male zebrafish. Exposure to 100 mg/L of PET fibers did not affect 17-beta estradiol, but significantly decreased the testosterone levels in male zebrafish. Sex hormone-related genes significantly decreased in both female and male zebrafish, except for androgen receptor in female zebrafish. However, these changes were exacerbated by the removal of NOM, suggesting a protective effect of NOM against PET fibers toxicity. We demonstrated that the accumulated PET fibers may lead to oxidative stress and sex hormone alteration, and disrupt the development of gonadal cells. Additionally, the NOM coating did not alter bioaccumulation considerably, but mitigated the adverse effects at the hormone level in PET fiber-exposed zebrafish. Thus, this study provides a basis for further research on the toxicity assessment of PET fibers and interactions between NOM and PET fiber-related toxicity.

Environmental toxicology of microplastic particles on fish: A review

The increase in plastic debris and its environmental impact has been a major concern for scientists. Physical destruction, chemical reactions, and microbial activity can degrade plastic waste into particles smaller than 5 mm, known as microplastics (MPs). MPs may eventually enter aquatic ecosystems through surface runoff. The accumulation of MPs in aquatic environments poses a potential threat to finfish, shellfish, and the ecological balance. This study investigated the effect of MP exposure on freshwater and marine fish. MPs could cause significant harm to fish, including physical damage, death, inflammation, oxidative stress, disruption of cell signalling and cellular biochemical processes, immune system suppression, genetic damage, and reduction in fish growth and reproduction rates. The activation of the detoxification system of fish exposed to MPs may be associated with the toxicity of MPs and chemical additives to plastic polymers. Furthermore, MPs can enhance the bioavailability of other xenobiotics, allowing these harmful substances to more easily enter and accumulate in fish. Accumulation of MPs and associated chemicals in fish can have adverse effects on the fish and humans who consume them, with these toxic substances magnifying as they move up the food chain. Changes in migration and reproduction patterns and disruptions in predator-prey relationships in fish exposed to MPs can significantly affect ecological dynamics. These interconnected changes can lead to cascading effects throughout aquatic ecosystems. Thus, implementing solutions like reducing plastic production, enhancing recycling efforts, using biodegradable materials, and improving waste management is essential to minimize plastic waste and its environmental impact.

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.

Detection of microplastics in human tissues and organs: A scoping review

Background

Research on microplastics has largely focused on the environment and marine organisms until recently. A growing body of evidence has detected microplastics in human organs and tissues, with their exact entry routes being unclear and their potential health effects remain unknown. This scoping review aimed to characterise microplastics in human tissues and organs, examine their entry routes and addressing gaps in research analytical techniques.

Methods

Eligibility criteria included English language full text articles, in-vivo human studies only, and searching the databases using pre-defined terms. We based our analysis and reporting on the PRISMA guideline and examined the quality of evidence using the risk of bias assessment tool.

Results

Of 3616 articles screened, 223 evaluated and 26 were eventually included in this review. Nine were high risk for bias, three were unclear risk and the rest low risk for bias. Microplastics were detected in 8/12 human organ systems including cardiovascular, digestive, endocrine, integumentary, lymphatic, respiratory, reproductive and urinary. Microplastics were also observed in other human biological samples such as breastmilk, meconium, semen, stool, sputum and urine. Microplastics can be characterised based on shape, colours, and polymer type. Potential entry routes into human included atmospheric inhalation and ingestion through food and water. The extraction techniques for analysis of microplastics in human tissues vary significantly, each offering distinct advantages and limitations.

Conclusions

Microplastics are commonly detected in human tissues and organs, with distinct characteristics and entry routes, and variable analytical techniques exist.

Potential mechanisms of aortic medial degeneration promoted by co-exposure to microplastics and lead

Microplastics (MPs) have attracted widespread attention because they can lead to combined toxicity by adsorbing heavy metals from the environment. Exposure to lead (Pb), a frequently adsorbed heavy metal by MPs, is common. In the current study, the coexistence of MPs and Pb was assessed in human samples. Then, mice were used as models to examine how co-exposure to MPs and Pb promotes aortic medial degeneration. The results showed that MPs and Pb co-exposure were detected in patients with aortic disease. In mice, MPs and Pb co-exposure promoted the damage of elastic fibers, loss of vascular smooth muscle cells (VSMCs), and release of inflammatory factors. In vitro cell models revealed that co-exposure to MPs and Pb induced excessive reactive oxygen species generation, impaired mitochondrial function, and triggered PANoptosome assembly in VSMCs. These events led to PANoptosis and inflammation through the cAMP/PKA-ROS signaling pathway. However, the use of the PKA activator 8-Br-cAMP or mitochondrial ROS scavenger Mito-TEMPO improved, mitochondrial function in VSMCs, reduced cell death, and inhibited inflammatory factor release. Taken together, the present study provided novel insights into the combined toxicity of MPs and Pb co-exposure on the aorta.

Combined exposure of PS-MPs with NaF induces Sertoli cell death and dysfunction via ferroptosis and apoptosis

The individual toxicity of sodium fluoride (NaF) and microplastics (MPs) has been extensively documented. Owing to their high specific surface area, widespread presence and durability, MPs can adsorb a broad spectrum of environmental contaminants into the organism. However, the combined toxicity of NaF and MPs has not been investigated. This study aimed to assess the effects of combined exposure to NaF and MPs on the function of testicular Sertoli cells (SCs) in male mice, and to investigate the underlying molecular mechanisms. The study revealed that combined exposure to NaF and MPs resulted in a decrease in the negative surface charge of MPs, along with an increase in the number of MPs entering the SCs. Through in vivo observation of the testicular pathological structure, spermatogenesis, and cell apoptosis in 180-day-old male mice, we discovered that combined exposure to NaF (80 mg/L) and MPs (10 mg/L) heightened reproductive toxicity compared to the individual exposure groups. This was evidenced by testicular structural defects, impaired spermatogenesis, and increased testicular cell apoptosis. Our in vitro studies showed that NaF (21 μg/mL) and MPs (100 μg/mL) synergistically induced SCs apoptosis and ferroptosis, leading to a reduction in SCs number and dysfunction. This ultimately resulted in structural and functional damage to the testes. Our findings demonstrate, for the first time, the synergistic effects of NaF and MPs on reproductive toxicity in mammals. These insights may provide valuable contributions to co-toxicity studies involving MPs and other environmental pollutants.

The Potential Mechanisms Involved in the Disruption of Spermatogenesis in Mice by Nanoplastics and Microplastics

BACKGROUND

Plastic-based products are ubiquitous due to their tremendous utility in our daily lives. Nanoplastic (NP) and microplastic (MP) pollution has become a severe threat to the planet and is a growing concern. It has been widely reported that polystyrene (PS) MPs are severely toxic to the male reproduction system, with effects including decreased sperm parameters, impaired spermatogenesis, and damaged testicular structures. However, the molecular mechanisms for impaired spermatogenesis remain poorly understood.

METHODS

C57BL/6 male mice were treated with PS-NPs (80 nm) and PS-MPs (5 μm) by oral gavage every day for 60 days. A series of morphological analyses were completed to explore the influence of PS-NP and PS-MP exposure on the testes. Compared to other cell types in the seminiferous tubule, PS-NP and PS-MP exposure can lead to decreased spermatocytes. Then, more refined molecular typing was further performed based on gene expression profiles to better understand the common and specific molecular characteristics after exposure to PS-NPs and PS-MPs.

RESULTS

There were 1794 common DEGs across the PS-NP groups at three different doses and 1433 common DEGs across the PS-MP groups at three different doses. GO and KEGG analyses of the common DEGs in the PS-NP and PS-MP groups were performed to enrich the common and specific functional progress and signaling pathways, including 349 co-enriched GO entries and 13 co-enriched pathways. Moreover, 348 GO entries and 33 pathways were specifically enriched in the PS-NP group, while 526 GO entries and 15 pathways were specifically enriched in the PS-MPs group.

CONCLUSIONS

PS-NPs were predominantly involved in regulating retinoic acid metabolism, whereas PS-MPs primarily influenced pyruvate metabolism and thyroid hormone metabolism. Our results highlight the different molecular mechanisms of PS-NPs and PS-MPs in the impairment of spermatogenesis in male mammals for the first time, providing valuable insights into the precise mechanisms of PS-NPs and PS-MPs in male reproduction.

Detrimental consequences of micropolymers associated plasticizers on endocrinal disruption

The prevalence of polymer usage in everyday activities has emerged as a detriment to both human life and the environment. A large number of studies describe severe impacts of micropolymers (MP) and nanopolymers (NP) on various organ systems, including the endocrine system. Additionally, plasticizers utilized as additives have been identified as endocrine-disrupting chemicals (EDCs). MP/NP, along with associated plasticizers, affect principal signalling pathways of endocrine glands such as the pituitary, thyroid, adrenal, and gonads, thereby disrupting hormone function and metabolic processes crucial for maintaining homeostasis, fertility, neural development, and fetal growth. This review delves into the sources, distribution, and effects of micropolymers, nanopolymers, and associated plasticizers acting as EDCs. Furthermore, it provides a detailed review of the mechanisms underlying endocrine disruption in relation to different types of MP/NP.

Chronic Polystyrene Microplastic Exposure Reduces Testosterone Levels in Mice through Mitochondrial Oxidative Stress and BAX/BCL2-Mediated Apoptosis

Microplastics (MPs) have emerged as a major environmental issue. They have been found to cause significant reproductive toxicity and lower testosterone levels in adult males, though the exact mechanisms remain unclear. In this study, C57bl/6 mice were orally exposed to saline or varying doses (0.25, 0.5, and 1 mg/day) of 5 μm polystyrene MPs (PS-MPs) for 4 weeks, and TM3 mouse Leydig cells were treated with different concentrations of PS-MPs. Our results found that exposure to PS-MPs significantly reduced testosterone levels and impaired the synthesis function of testicular steroids. In vitro, PS-MPs reduced steroid synthesis in Leydig cells. Treatment with PS-MPs significantly increased the apoptosis rate and BAX/BCL2 ratio in Leydig cells. Additionally, GSH-px and SOD activities decreased, while MDA levels increased, along with a rise in mitochondrial ROS. In conclusion, chronic PS-MP exposure reduced testosterone levels in mice through mitochondrial oxidative stress and BAX/BCL2-mediated apoptosis. This study offers new insights into the health risks posed by MPs.

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.

Polystyrene nanoplastics exposure causes erectile dysfunction in rats

Polystyrene nanoplastics (PS-NPs), emerging and increasingly pervasive environmental contaminants, have the potential to cause persistent harm to organisms. Although previous reports have documented local accumulation and adverse effects in a variety of major organs after PS-NPs exposure, the impact of PS-NPs exposure on erectile function remains unexplored. Herein, we established a rat model of oral exposure to 100 nm PS-NPs for 28 days. To determine the best dose range of PS-NPs, we designed both low-dose and high-dose PS-NPs groups, which correspond to the minimum and maximum human intake doses, respectively. The findings indicated that PS-NPs could accumulate within the corpus cavernosum and high dose but not low dose of PS-NPs triggered erectile dysfunction. Moreover, the toxicological effects of PS-NPs on erectile function include fibrosis in the corpus cavernous, endothelial dysfunction, reduction in testosterone levels, elevated oxidative stress and apoptosis. Overall, this study revealed that PS-NPs exposure can cause erectile dysfunction via multiple ways, which provided new insights into the toxicity of PS-NPs.

MicroRNA and Gut Microbiota Alter Intergenerational Effects of Paternal Exposure to Polyethylene Nanoplastics

Nanoplastics (NPs), as emerging contaminants, have been shown to cause testicular disorders in mammals. However, whether paternal inheritance effects on offspring health are involved in NP-induced reproductive toxicity remains unclear. In this study, we developed a mouse model where male mice were administered 200 nm polyethylene nanoparticles (PE-NPs) at a concentration of 2 mg/L through daily gavage for 35 days to evaluate the intergenerational effects of PE-NPs in an exclusive male-lineage transmission paradigm. We observed that paternal exposure to PE-NPs significantly affected growth phenotypes and sex hormone levels and induced histological damage in the testicular tissue of both F0 and F1 generations. In addition, consistent changes in sperm count, motility, abnormalities, and gene expression related to endoplasmic reticulum stress, sex hormone synthesis, and spermatogenesis were observed across paternal generations. The upregulation of microRNA (miR)-1983 and the downregulation of miR-122-5p, miR-5100, and miR-6240 were observed in both F0 and F1 mice, which may have been influenced by reproductive signaling pathways, as indicated by the RNA sequencing of testis tissues and quantitative real-time polymerase chain reaction findings. Furthermore, alterations in the gut microbiota and subsequent Spearman correlation analysis revealed that an increased abundance of Desulfovibrio (C21_c20) and Ruminococcus (gnavus) and a decreased abundance of Allobaculum were positively associated with spermatogenic dysfunction. These findings were validated in a fecal microbiota transplantation trial. Our results demonstrate that changes in miRNAs and the gut microbiota caused by paternal exposure to PE-NPs mediated intergenerational effects, providing deeper insights into mechanisms underlying the impact of paternal inheritance.

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.

Navigating the nexus: climate dynamics and microplastics pollution in coastal ecosystems

Microplastics (MPs) pollution is an emerging environmental health concern, impacting soil, plants, animals, and humans through their entry into the food chain via bioaccumulation. Human activities such as improper solid waste dumping are significant sources that ultimately transport MPs into the water bodies of the coastal areas. Moreover, there is a complex interplay between the coastal climate dynamics, environmental factors, the burgeoning issue of MPs pollution and the complex web of coastal pollution. We embark on a comprehensive journey, synthesizing the latest research across multiple disciplines to provide a holistic understanding of how these inter-connected factors shape and reshape the coastal ecosystems. The comprehensive review also explores the impact of the current climatic patterns on coastal regions, the intricate pathways through which MPs can infiltrate marine environments, and the cascading effects of coastal pollution on ecosystems and human societies in terms of health and socio-economic impacts in coastal regions. The novelty of this review concludes the changes in climate patterns have crucial effects on coastal regions, proceeding MPs as more prevalent, deteriorating coastal ecosystems, and hastening the transfer of MPs. The continuous rising sea levels, ocean acidification, and strong storms result in habitat loss, decline in biodiversity, and economic repercussion. Feedback mechanisms intensify pollution effects, underlying the urgent demand for environmental conservation contribution. In addition, the complex interaction between human, industry, and biodiversity demanding cutting edge strategies, innovative approaches such as remote sensing with artificial intelligence for monitoring, biobased remediation techniques, global cooperation in governance, policies to lessen the negative socioeconomic and environmental effects of coastal pollution.

Gender-specific effects of polystyrene nanoplastic exposure on triclosan-induced reproductive toxicity in zebrafish (Danio rerio)

Nanoplastics (NPs) and triclosan (TCS) are ubiquitous emerging environmental contaminants detected in human samples. While the reproductive toxicity of TCS alone has been studied, its combined effects with NPs remain unclear. Herein, we employed Fourier transform infrared spectroscopy and dynamic light scattering to characterize the coexposure of polystyrene nanoplastics (PS-NPs, 50 nm) with TCS. Then, adult zebrafish were exposed to TCS at environmentally relevant concentrations (0.361-48.2 μg/L), with or without PS-NPs (1.0 mg/L) for 21 days. TCS biodistribution in zebrafish tissues was investigated using ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry. Reproductive toxicity was assessed through gonadal histopathology, fertility tests, changes in steroid hormone synthesis and gene expression within the hypothalamus-pituitary-gonad-liver (HPGL) axis. Transcriptomics and proteomics were applied to explore the underlying mechanisms. The results showed that PS-NPs could adsorb TCS, thus altering the PS-NPs' physical characteristics. Our observations revealed that coexposure with PS-NPs reduced TCS levels in the ovaries, livers, and brains of female zebrafish. Conversely, in males, coexposure with PS-NPs increased TCS levels in the testes and livers, while decreasing them in the brain. We found that co-exposure mitigated TCS-induced ovary development inhibition while exacerbated TCS-induced spermatogenesis suppression, resulting in increased embryonic mortality and larval malformations. This co-exposure influenced the expression of genes linked to steroid hormone synthesis (cyp11a1, hsd17β, cyp19a1) and attenuated the TCS-decreased estradiol (E2) in females. Conversely, testosterone levels were suppressed, and E2 levels were elevated due to the upregulation of specific genes (cyp11a1, hsd3β, cyp19a1) in males. Finally, the integrated analysis of transcriptomics and proteomics suggested that the aqp12-dctn2 pathway was involved in PS-NPs' attenuation of TCS-induced reproductive toxicity in females, while the pck2-katnal1 pathway played a role in PS-NPs' exacerbation of TCS-induced reproductive toxicity in males. Collectively, PS-NPs altered TCS-induced reproductive toxicity by disrupting the HPGL axis, with gender-specific effects.

The association and underlying mechanism of the digit ratio (2D:4D) in hypospadias

The second-to-fourth digit (2D:4D) ratio is thought to be associated with prenatal androgen exposure. However, the relationship between the 2D:4D ratio and hypospadias is poorly understood, and its molecular mechanism is not clear. In this study, by analyzing the hand digit length of 142 boys with hypospadias (23 distal, 68 middle, and 51 proximal) and 196 controls enrolled in Shanghai Children's Hospital (Shanghai, China) from December 2020 to December 2021, we found that the 2D:4D ratio was significantly increased in boys with hypospadias ( P < 0.001) and it was positively correlated with the severity of the hypospadias. This was further verified by the comparison of control mice and prenatal low testosterone mice model obtained by knocking out the risk gene (dynein axonemal heavy chain 8 [ DNAH8 ]) associated with hypospadias. Furthermore, the discrepancy was mainly caused by a shift in 4D. Proteomic characterization of a mouse model validated that low testosterone levels during pregnancy can impair the growth and development of 4D. Comprehensive mechanistic explorations revealed that during the androgen-sensitive window, the downregulation of the androgen receptor (AR) caused by low testosterone levels, as well as the suppressed expression of chondrocyte proliferation-related genes such as Wnt family member 5a ( Wnt5a ), Wnt5b , Smad family member 2 ( Smad2 ), and Smad3 ; mitochondrial function-related genes in cartilage such as AMP-activated protein kinase ( AMPK ) and nuclear respiratory factor 1 ( Nrf-1 ); and vascular development-related genes such as myosin light chain ( MLC ), notch receptor 3 ( Notch3 ), and sphingosine kinase 1 ( Sphk1 ), are responsible for the limitation of 4D growth, which results in a higher 2D:4D ratio in boys with hypospadias via decreased endochondral ossification. This study indicates that the ratio of 2D:4D is a risk marker of hypospadias and provides a potential molecular mechanism.

Subchronic co-exposure of polystyrene nanoplastics and 3-BHA significantly aggravated the reproductive toxicity of ovaries and uterus in female mice

Both nanoplastics (NPs) and 3-tert-butyl-4-hydroxyanisole (3-BHA) are environmental contaminants that can bio-accumulate through the food chain. However, the combined effects of which on mammalian female reproductive system remain unclear. Here, the female ICR-CD1 mice were used to evaluate the damage effects of ovaries and uterus after NPs and 3-BHA co-treatment for 35 days. Firstly, co-exposure significantly reduced the body weight and organ index of ovaries and uterus in mice. Secondly, combined effects of NPs and 3-BHA exacerbated the histopathological abnormalities to the ovaries and uterus and decreased female sex hormones such as FSH and LH while increased antioxidant activities including CAT and GSH-Px. Moreover, the apoptotic genes, inflammatory cytokines and the key reproductive development genes such as FSTL1 were significantly up-regulated under co-exposure conditions. Thirdly, through transcriptional and bioinformatics analysis, immunofluorescence and western blotting assays, together with molecular docking simulation, we determined that co-exposure up-regulated the FSTL1, TGF-β and p-Smad1/5/9 but down-regulated the expression of BMP4. Finally, the pharmacological rescue experiments further demonstrated that co-exposure of NPs and 3-BHA mainly exacerbated the female reproductive toxicity through FSTL1-mediated BMP4/TGF-β/SMAD signaling pathway. Taken together, our studies provided the theoretical basis of new environmental pollutants on the reproductive health in female mammals.

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.

Reproductive toxicity of PFOA, PFOS and their substitutes: A review based on epidemiological and toxicological evidence

Per- and polyfluoroalkyl substances (PFAS) have already drawn a lot of attention for their accumulation and reproductive toxicity in organisms. Perfluorooctanoic acid (PFOA) and perfluorooctanoic sulfonate (PFOS), two representative PFAS, are toxic to humans and animals. Due to their widespread use in environmental media with multiple toxicities, PFOA and PFOS have been banned in numerous countries, and many substitutes have been produced to meet market requirements. Unfortunately, most alternatives to PFOA and PFOS have proven to be cumulative and highly toxic. Of the reported multiple organ toxicities, reproductive toxicity deserves special attention. It has been confirmed through epidemiological studies that PFOS and PFOA are not only associated with reduced testosterone levels in humans, but also with an association with damage to the integrity of the blood testicular barrier. In addition, for women, PFOA and PFOS are correlated with abnormal sex hormone levels, and increase the risk of infertility and abnormal menstrual cycle. Nevertheless, there is controversial evidence on the epidemiological relationship that exists between PFOA and PFOS as well as sperm quality and reproductive hormones, while the evidence from animal studies is relatively consistent. Based on the published papers, the potential toxicity mechanisms for PFOA, PFOS and their substitutes were reviewed. For males, PFOA and PFOS may produce reproductive toxicity in the following five ways: (1) Apoptosis and autophagy in spermatogenic cells; (2) Apoptosis and differentiation disorders of Leydig cells; (3) Oxidative stress in sperm and disturbance of Ca2+ channels in sperm membrane; (4) Degradation of delicate intercellular junctions between Sertoli cells; (5) Activation of brain nuclei and shift of hypothalamic metabolome. For females, PFOA and PFOS may produce reproductive toxicity in the following five ways: (1) Damage to oocytes through oxidative stress; (2) Inhibition of corpus luteum function; (3) Inhibition of steroid hormone synthesis; (4) Damage to follicles by affecting gap junction intercellular communication (GJIC); (5) Inhibition of placental function. Besides, PFAS substitutes show similar reproductive toxicity with PFOA and PFOS, and are even more toxic to the placenta. Finally, based on the existing knowledge, future developments and direction of efforts in this field are suggested.

A systematic review of microplastics emissions in kitchens: Understanding the links with diseases in daily life

The intensification of microplastics (MPs) pollution has emerged as a formidable environmental challenge, with profound global implications. The pervasive presence of MPs across a multitude of environmental mediums, such as the atmosphere, soil, and oceans, extends to commonplace items, culminating in widespread human ingestion and accumulation via channels like food, water, and air. In the domestic realm, kitchens have become significant epicenters for MPs pollution. A plethora of kitchen utensils, encompassing coated non-stick pans, plastic cutting boards, and disposable utensils, are known to release substantial quantities of MPs particles in everyday use, which can then be ingested alongside food. This paper conducts a thorough examination of contemporary research addressing the release of MPs from kitchen utensils during usage and focuses on the health risks associated with MPs ingestion, as well as the myriad factors influencing the release of MPs in kitchen utensils. Leveraging the insights derived from this analysis, this paper proposes a series of strategic recommendations and measures targeted at mitigating the production of MPs in kitchen settings. These initiatives are designed not solely to diminish the release of MPs but also to enhance public awareness regarding this pressing environmental concern. By adopting more informed practices in kitchens, we can significantly contribute to the reduction of the environmental burden of MPs pollution, thus safeguarding both human health and the ecological system.

Polystyrene microplastics induce male reproductive toxicity in mice by activating spermatogonium mitochondrial oxidative stress and apoptosis

Microplastics have emerged as environmental hazards in recent years. This study was intended to prove the toxic effects of microplastics on the male reproductive system and further elucidate its mechanism. C57bl/6 mice were exposed to ultrapure water or different doses (0.25, 0.5 and 1 mg/d) of 5 μm polystyrene microplastics (PS-MPs) for 4 weeks, and the GC-1 mouse spermatogonium was treated with different concentrations of PS-MPs. The results showed that sperm count and motility were decreased, and sperm deformity rate was increased after exposure to PS-MPs. The morphology of testes in PS-MPs groups exhibited pathological changes, such as abnormal development of spermatogenic tubules, and inhibited spermatogonium function. Furthermore, the fluorescence intensity of TUNEL staining and the BAX/BCL2 ratio were increased. Exposure to PS-MPs resulted in impaired mitochondrial morphology of spermatogonium, decreased activity of GSH-px and SOD, and increased the MDA level. In vitro, after treatment with PS-MPs, the cell apoptosis rate of spermatogonium was significantly increased, mitochondrial membrane potential was decreased, mitochondrial morphology was damaged, and exposure to PS-MPs increased mitochondrial reactive oxygen species, inducing an oxidative stress state in spermatogonia. In summary, PS-MPs induced a decrease in sperm quality by activating spermatogonium mitochondrial oxidative stress and apoptosis, offering novel insights into mitigating the reproductive toxicity of microplastics.

Melatonin counteracts polyethylene microplastics induced adreno-cortical damage in male albino rats

There are various substances that can disrupt the homeostatic mechanisms of the body, defined as endocrine-disrupting chemicals (EDCs). The persistent nature of microplastics (MPs) is a cause for concern due to their ability to accumulate in food chains and widespread use, making their toxic effects particularly alarming. The potential of MPs for disrupting the endocrine system was observed in multiple tissues. Moreover, the adrenal gland is known to be extremely sensitive to EDCs, while with the effect of MPs on the adrenal gland has not previously been studied. This study aimed to highlight the potential polyethylene microplastics (PE-MPs) induced adreno-toxic effects rather than exploring the implicated mechanisms and concluding if melatonin (Mel) can afford protection against PE-MPs induced adreno-toxicity. To fulfill the goal, six groups of rats were used; control, Mel, PE-MPs (3.75 mg/kg), PE-MPs (15 mg/kg), PE-MPs (3.75 mg/kg) +Mel, and PE-MPs (15 mg/kg) +Mel. PE-MPs induced toxic changes in the adrenal cortex, which was evident by increased adrenal weight, histopathological examination, and ultrastructural changes detected by electron microscope. A reduction in serum cortisol and an increase in serum adrenocorticotropic hormone resulted from the adreno-toxic effects of PE-MPs. Mechanisms may include the reduction of steroidogenesis-related genes, as PE-MPs drastically reduce mRNA levels of StAR, Nr0b1, Cyp11A1, as well as Cyp11B1. Also, oxidative stress that results from PE-MPs is associated with higher rates of lipid peroxidation and decreased superoxide dismutase and glutathione. PE-MPs inflammatory effect was illustrated by elevated expression of IL-1β and NF-ķB, detected by immunohistochemical staining, in addition to increased expression of caspase-3 and mRNA of Bax, markers of proapoptotic activity. The impacts of PE-MPs were relatively dose-related, with the higher dose showing more significant toxicity than the lower one. Mel treatment was associated with a substantial amelioration of PE-MPs-induced toxic changes. Collectively, this study fills the knowledge gap about the MPs-induced adrenal cortex and elucidates various related toxic mechanisms. It also supports Mel's potential protective activity through antioxidant, anti-inflammatory, anti-apoptotic, and gene transcription regulatory effects.

Polystyrene nanoplastics exposure triggers spermatogenic cell senescence via the Sirt1/ROS axis

Polystyrene nanoplastics (PS-NPs) have been reported to accumulate in the testes and constitute a new threat to reproductive health. However, the exact effects of PS-NPs exposure on testicular cells and the underlying mechanisms remain largely unknown. The C57BL/6 male mice were orally administered with PS-NPs (80 nm) at different dosages (0, 10, and 40 mg/kg/day) for 60 days, and GC-1 cells were treated with PS-NPs in this study. Enlarged seminiferous tubule lumens and a loose and vacuolated layer of spermatogenic cells were observed in PS-NPs-exposed mice. Spermatogenic cells which may be one of the target cells for this reproductive damage, were decreased in the mice from PS-NPs group. PS-NPs caused spermatogenic cells to undergo senescence, manifested as elevated SA-β-galactosidase activity and activated senescence-related signaling p53-p21/Rb-p16 pathways, and induced cell cycle arrest. Mechanistically, Gene Ontology (GO) enrichment suggested the key role of reactive oxygen species (ROS) in PS-NPs-induced spermatogenic cell senescence, and this result was confirmed by measuring ROS levels. Moreover, ROS inhibition partially attenuated the senescence phenotype of spermatogenic cells and DNA damage. Using the male health atlas (MHA) database, Sirt1 was filtrated as the critical molecule in the regulation of testicular senescence. PS-NPs induced overexpression of the main ROS generator Nox2, downregulated Sirt1, increased p53 and acetylated p53 in vivo and in vitro, whereas these disturbances were partially restored by pterostilbene. In addition, pterostilbene intervention significantly alleviated the PS-NPs-induced spermatogenic cell senescence and attenuated ROS burst. Collectively, our study reveals that PS-NPs exposure can trigger spermatogenic cell senescence mediated by p53-p21/Rb-p16 signaling by regulating the Sirt1/ROS axis. Importantly, pterostilbene intervention may be a promising strategy to alleviate this damage.

Vertebrate response to microplastics, nanoplastics and co-exposed contaminants: Assessing accumulation, toxicity, behaviour, physiology, and molecular changes

Pollution from microplastics (MPs) and nanoplastics (NPs) has gained significant public attention and has become a serious environmental problem worldwide. This review critically investigates MPs/NPs' ability to pass through biological barriers in vertebrate models and accumulate in various organs, including the brain. After accumulation, these particles can alter individuals' behaviour and exhibit toxic effects by inducing oxidative stress or eliciting an inflammatory response. One major concern is the possibility of transgenerational harm, in which toxic consequences are displayed in offspring who are not directly exposed to MPs/NPs. Due to their large and marked surface hydrophobicity, these particles can easily absorb and concentrate various environmental pollutants, which may increase their toxicity to individuals and subsequent generations. This review systematically provides an analysis of recent studies related to the toxic effects of MPs/NPs, highlighting the intricate interplay between co-contaminants in vitro and in vivo. We further delve into mechanisms of MPs/NPs-induced toxicity and provide an overview of potential therapeutic approaches to lessen the negative effects of these MPs/NPs. The review also emphasizes the urgency of future studies to examine the long-term effects of chronic exposure to MPs/NPs and their size- and type-specific hazardous dynamics, and devising approaches to safeguard the affected organisms.

Application of organoid technology in the human health risk assessment of microplastics: A review of progresses and challenges

Microplastic (MP) pollution has become a global environmental issue, and increasing concern has been raised about its impact on human health. Current studies on the toxic effects and mechanisms of MPs have mostly been conducted in animal models or in vitro cell cultures, which have limitations regarding inter-species differences or stimulation of cellular functions. Organoid technology derived from human pluripotent or adult stem cells has broader prospects for predicting the potential health risks of MPs to humans. Herein, we reviewed the current application advancements and opportunities for different organoids, including brain, retinal, intestinal, liver, and lung organoids, to assess the human health risks of MPs. Organoid techniques accurately simulate the complex processes of MPs and reflect phenotypes related to diseases caused by MPs such as liver fibrosis, neurodegeneration, impaired intestinal barrier and cardiac hypertrophy. Future perspectives were also proposed for technological innovation in human risk assessment of MPs using organoids, including extending the lifespan of organoids to assess the chronic toxicity of MPs, and reconstructing multi-organ interactions to explore their potential in studying the microbiome-gut-brainaxis effect of MPs.

Multi-omics reveals the testosterone promotion effect mechanism of Cordyceps Sobolifera on Leydig cells

ETHNOPHARMACOLOGICAL RELEVANCE

Cordyceps sobolifera (CS) has been traditionally utilized as an ethnic remedy for various health conditions, including chronic kidney diseases, anti-fatigue interventions, and management of chronic inflammation. Notably, CS is recognized for its substantial content of bioactive compounds, among which nucleosides prominently feature as constituents with diverse therapeutic advantages.

AIM OF THE STUDY

This study aims to investigate the effects of CS on testosterone secretion in Leydig cells and explore the underlying mechanism.

MATERIALS AND METHODS

Leydig cells were isolated from rat testes to establish a primary rat Leydig cells model. Cell proliferation and testosterone secretion were assessed via the methyl-piperidino-pyrazole (MTT) assay and enzyme-linked immunosorbent assay (ELISA), respectively. Samples earmarked for RNA sequencing (RNA-Seq) analysis facilitated the identification of significantly differentially expressed genes (DEGs), and we conducted Gene Ontology (GO)/Kyoto Encyclopedia of Genes and Genomes (KEGG) functional annotation and enrichment analyses. The veracity of our findings was validated through quantitative real time polymerase chain reaction (qRT-PCR) and western blotting.

RESULTS

The results showed that CS and guanosine could promote Leydig cell proliferation and bolster testosterone secretion. Our integrative analysis of metabolomics and transcriptomics has unveiled the potential mechanisms governing testosterone synthesis. Specifically, metabolomics has illuminated striking correlations within cholesterol metabolism, and bile secretion. Concurrently, transcriptomics has underscored the pivotal roles played by the cyclic adenosine monophosphate (cAMP) signaling pathway and steroid hormone biosynthesis. Furthermore, our investigation has demonstrated CS's aptitude in elevating the expression of proteins and genes. Notably, our findings have elucidated that these effects can be mitigated by protein kinase A (PKA) and adenylate cyclase (AC) specific inhibitors.

CONCLUSION

This study delineates the cAMP-PKA pathways as plausible mechanisms underpinning the testosterone-enhancing properties of CS, with guanosine emerging as a fundamental bioactive constituent.

A metabolomic perspective on the mechanisms by which environmental pollutants and lifestyle lead to male infertility

The incidence of male infertility (MI) is rising annually. According to epidemiological studies, environmental pollution (e.g., organic, inorganic, and air pollutants), occupational exposure (e.g., high temperature, organic solvents, and pesticides), and poor lifestyle (e.g., diet, sleep, smoking, alcohol consumption, and exercise) are important non-genetic causative factors of MI. Due to multiple and complex causative factors, the dose-effect relationship, and the uncertainty of pathogenicity, the pathogenesis of MI is far from fully clarified. Recent data show that the pathogenesis of MI can be monitored by the metabolites in serum, seminal plasma, urine, testicular tissue, sperm, and other biological samples. It is considered that these metabolites are closely related to MI phenotypes and can directly reflect the individual pathological and physiological conditions. Therefore, qualitative and quantitative analysis of the metabolome, the related metabolic pathways, and the identification of biomarkers will help to explore the MI-related metabolic problems and provide valuable insights into its pathogenic mechanisms. Here, we summarized new findings in MI metabolomics biomarkers research and their abnormal metabolic pathways triggered by the presented non-genetic risk factors, providing a metabolic landscape of semen and seminal plasma in general MI patients. Then, we compared the similarities and differences in semen and seminal plasma biomarkers between MI patients exposed to environmental and poor lifestyle factors and MI patients in general, and summarized some common biomarkers. We provide a better understanding of the biological underpinnings of MI pathogenesis, which might offer novel diagnostic, prognostic, and precise treatment approaches to MI.

Toxicological Research on Nano and Microplastics in Environmental Pollution: Current Advances and Future Directions

This review explains the sources of nanoplastics (NPs) and microplastics (MPs), their release, fate, and associated health risks in the aquatic environment. In the 21st century, scientists are grappling with a major challenge posed by MPs and NPs. The global production of plastic has skyrocketed from 1.5 million tons in the 1950s to an astonishing 390.7 million tons in 2021. This pervasive presence of these materials in our environment has spurred scientific inquiry into their potentially harmful effects on living organisms. Studies have revealed that while MPs, with their larger surface area, are capable of absorbing contaminants and pathogens from the surroundings, NPs can easily be transferred through the food chain. As a result, living organisms may ingest them and accumulate them within their bodies. Due to their minuscule size, NPs are particularly difficult to isolate and quantify. Furthermore, exposure to both NPs and MPs has been linked to various adverse health effects in aquatic species, including neurological impairments, disruption of lipid and energy metabolism, and increased susceptibility to cytotoxicity, oxidative stress, inflammation, and reactive oxygen species (ROS) production. It is alarming to note that MPs have even been detected in commercial fish, highlighting the severity of this issue. There are also challenges associated with elucidating the toxicological effects of NPs and MPs, which are discussed in detail in this review. In conclusion, plastic pollution is a pressing issue that governments should tackle by ensuring proper implementation of rules and regulations at national and provincial levels to reduce its health risks.

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.

Liver Injury Induced by Exposure to Polystyrene Microplastics Alone or in Combination with Cadmium in Mice Is Mediated by Oxidative Stress and Apoptosis

Microplastics (MPs) have been considered an emerging environmental pollutant which, when combined with toxic metals, enter the circulatory system of mammals and eventually cause damage. Therefore, it is important to study the toxicity of the mixture of MPs and heavy metals for evaluating risk assessment of mammals. In the present study, the toxicological effects of different concentrations of polystyrene (PS)-MPs alone or in combination with cadmium chloride (CdCl2) during chronic exposure (8 weeks) were evaluated using intragastric administration in mice. Using comparative analysis, it was revealed that PS-MPs alone or in combination with Cd could destroy the normal structural morphology of liver tissue and increase the levels of two biochemical indicators of liver damage, thereby inducing changes in antioxidant and hyperoxide capacities. In addition, PS-MPs and/or Cd activated the antioxidant signaling pathway Nrf2-Keap1 and affected the endogenous apoptosis signaling pathway p53-Bcl-2/Bax, thus promoting apoptosis. These findings suggested that exposure to MPs alone or in combination with Cd led to adverse effects on the liver. Furthermore, it was revealed that co-exposure to MPs and Cd reduced Cd toxicity, thereby highlighting the possibility MPs may act as carriers of other toxic substances and coordinate with them. Therefore, evaluating the synergistic or anti-agonistic effects of MPs on the toxicity and bioavailability of xenobiotics is in the future critical in environmental toxicological studies.

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.

Atlas and source of the microplastics of male reproductive system in human and mice

Regarding the impact of microplastics (MPs) on the male reproductive system, previous studies have identified a variety of MPs in both human semen and testicular samples. These studies have put forward the hypothesis that small particles can enter the semen through the epididymis and seminal vesicles. Here, we performed qualitative and quantitative analyses of MPs in human testis, semen, and epididymis samples, as well as in testis, epididymis, seminal vesicle, and prostate samples from mice via pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). The goal of this approach was to comprehensively characterize the distribution of MPs within the male reproductive system. Additionally, we aimed to evaluate potential sources of MPs identified in semen, as well as to identify possible sources of overall MP exposure. Our results highlighted a general atlas of MPs in the male reproductive system and suggested that MPs in semen may originate from the epididymis, seminal vesicles, and prostate. An exposure questionnaire, coupled with the characteristics of the MPs detected in the male reproductive system, revealed that high urbanization, home-cooked meals, and using scrub cleansers were important sources of MP exposure in men. These findings may provide novel insights into alleviating the exposure of men to MPs.

Exploring the impact of polystyrene microplastics on human health: unravelling the health implications of polystyrene microplastics (PS-MPs): a comprehensive study on cytotoxicity, reproductive health, human exposure, and exposure assessment

This investigation explores the various impacts that polystyrene microplastics (PS-MPs) have on human health. As most of the plastic materials affect human health when they release leachable toxic substances that affect human health, this causes a negative effect that determines poor health conditions and leads to health hazards associated with plastic toxins routed in the human body, such as: Polychlorinated Biphenyls, Polybrominated Biphenyls etc. The study includes micro-plastic exposure assessment on testicular structure analysis, and cytotoxicity evaluations of different human cell types. The findings clarified the possible dangers of PS-MPs exposure from food, medications, and common products, emphasising the necessity of standard specimen handling procedures for precise biomonitoring.

Prenatal DEHP exposure induces lifelong testicular toxicity by continuously interfering with steroidogenic gene expression

Background

Epidemiologic studies suggested the association between prenatal di-(2-ethylhexyl) phthalate (DEHP) exposure and disorders of sex development (DSD), adult male disorders, and reproductive aging. Inhibiting testosterone synthesis by interfering with steroidogenic gene expression induces testicular toxicity, however, whether prenatal DEHP exposure induces testicular toxicity through this mechanism remains uncertain.

Methods

C57BL/6JGpt male mice underwent different doses (0, 100, 500, 1,000 mg/kg) of prenatal DEHP exposure during gestational day 10 to delivery day, the testicular toxicity (genital development, testosterone, semen quality, and morphology of testis tissue) in the neonatal, post-puberal and middle-aged stages was observed, and the steroidogenic gene (Lhcgr, Star, Cyp11a1, Cyp17a1, Hsd17b3, and Hsd3b2) expression was analyzed by quantitative polymerase chain reaction (qPCR) and Western blot (WB). The interference of steroidogenic gene expression in TM3 cells after mono-(2-ethylhexyl) phthalate (MEHP) exposure was also explored for verification.

Results

Prenatal DEHP exposure induced immediate testicular injury in the neonatal stage [reduced anogenital distance (AGD) and intratesticular testosterone], DSD in the post-puberal stage (poor genital development), and reproductive aging in the middle-aged stage (obesity, reduced testosterone and semen quality, and atrophic seminiferous tubules), especially in the high dose. Prenatal DEHP exposure continuously interfered with steroidogenic gene expression (Hsd3b2, Hsd17b3) in RNA and protein levels. MEHP inhibited testosterone synthesis of TM3 cells by interfering with steroidogenic gene expression (Hsd3b2, Hsd17b3) in RNA and protein levels.

Conclusions

Prenatal DEHP exposure induces lifelong testicular toxicity by continuously interfering with steroidogenic gene expression, thus indicating the association between prenatal exposure and DSD, adult male disorders, and reproductive aging.

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.

Dichloroacetic acid and trichloroacetic acid as disinfection by-products in drinking water are endocrine-disrupting chemicals

Dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) are two typical non-volatile disinfection by-products (DBPs) found in drinking water. Increasing evidence has demonstrated that they show reproductive toxicity. However, whether they might have endocrine disrupting properties remains largely unknown. To discover this, we treated male mice or pregnant mice with 0, 1-, 102-, 103-, 104-, or 5 × 104-fold maximal concentration level (MCL) of DCAA or TCAA in drinking water. In male mice, the levels of testosterone in serum and androgen receptor (AR) in testis were declined with ≥ 103-fold MCL of DCAA (26.4 mg/kg/d) or TCAA (52.7 mg/kg/d). In pregnant mice, miscarriage rates were increased with ≥ 104-fold MCL of DCAA (264 mg/kg/d) or ≥ 103-fold MCL of TCAA. The levels of FSH in serum were increased and those of estradiol and progesterone were reduced with ≥ 103-fold MCL of DCAA or TCAA. The protein levels of estrogen receptors (ERα and ERβ) in ovary were reduced with ≥ 102-fold MCL of DCAA (2.64 mg/kg/d) or TCAA (5.27 mg/kg/d). Exposure to some certain fold MCL of DCAA or TCAA also altered the protein levels of ERα and ERβ in uterus and placenta. Exposure to 5 × 104-fold MCL of both DCAA and TCAA showed the combined effects. Therefore, both DCAA and TCAA could be considered as novel reproductive endocrine disrupting chemicals, which might be helpful for further assessment of the toxicological effects of DCAA and TCAA and the awareness of reproductive endocrine disrupting properties caused by DCAA and TCAA in drinking water.

Exposure to high dose of polystyrene nanoplastics causes trophoblast cell apoptosis and induces miscarriage

BACKGROUND

With rapid increase in the global use of various plastics, microplastics (MPs) and nanoplastics (NPs) pollution and their adverse health effects have attracted global attention. MPs have been detected out in human body and both MPs and NPs showed female reproductive toxicological effects in animal models. Miscarriage (abnormal early embryo loss), accounting for 15-25% pregnant women worldwide, greatly harms human reproduction. However, the adverse effects of NPs on miscarriage have never been explored.

RESULTS

In this study, we identified that polystyrene (PS) plastics particles were present in women villous tissues. Their levels were higher in villous tissues of unexplained recurrent miscarriage (RM) patients vs. healthy control (HC) group. Furthermore, mouse assays further confirmed that exposure to polystyrene nanoplastics (PS-NPs, 50 nm in diameter, 50 or 100 mg/kg) indeed induced miscarriage. In mechanism, PS-NPs exposure (50, 100, 150, or 200 µg/mL) increased oxidative stress, decreased mitochondrial membrane potential, and increased apoptosis in human trophoblast cells by activating Bcl-2/Cleaved-caspase-2/Cleaved-caspase-3 signaling through mitochondrial pathway. The alteration in this signaling was consistent in placental tissues of PS-NPs-exposed mouse model and in villous tissues of unexplained RM patients. Supplement with Bcl-2 could efficiently suppress apoptosis in PS-NPs-exposed trophoblast cells and reduce apoptosis and alleviate miscarriage in PS-NPs-exposed pregnant mouse model.

CONCLUSIONS

Exposure to PS-NPs activated Bcl-2/Cleaved-caspase-2/Cleaved-caspase-3, leading to excessive apoptosis in human trophoblast cells and in mice placental tissues, further inducing miscarriage.

Microplastic-induced inhibition of cell adhesion and toxicity evaluation using human dermal fibroblast-derived spheroids

Nanoplastics and microplastics (MPs) can significantly affect marine ecosystems and pose potential risks to human health. Although adverse effects stemming from direct exposure to MPs have been demonstrated at the cellular level in animal models, the potential toxicity of these materials in the human body remains uncertain. In this study, we investigated the three-dimensional (3D) behavior of dermal-derived cells exposed to MPs using artificially manufactured spherical primary polystyrene (PS) particles. To explore these effects, we used cellular spheroids as a 3D cell culture model, examined the size-dependent penetration of PS-MPs, and observed morphological alterations in the spheroids. Furthermore, we assessed changes in physiological activities, including reactive oxygen species, adenosine triphosphate, and lactate dehydrogenase, to elucidate the potential intra- and extracellular toxic reactions to PS-MPs. Additionally, our examination of cell-cell junctions and the extracellular matrix (ECM), along with analysis of the regulators involved in their decreased integrity, revealed negatively influenced changes in expression. This exposure study using spheroid models provides new insights into the potential toxicity of short-term exposure to MPs under conditions that closely resemble in vivo systems.

A meta-analysis-based adverse outcome pathway for the male reproductive toxicity induced by microplastics and nanoplastics in mammals

The male reproductive toxicity of microplastics (MPs) and nanoplastics (NPs) has attracted great attention, but the latent mechanisms remain fragmented. This review performed the adverse outcome pathway (AOP) analysis and meta-analysis in 39 relevant studies, with the AOP analysis to reveal the cause-and-effect relationships of MPs/NPs-induced male reproductive toxicity and the meta-analysis to quantify the toxic effects. In the AOP framework, increased reactive oxygen species (ROS) is the molecular initiating event (MIE), which triggered several key events (KEs) at different levels. At the cellular level, the KEs included oxidative stress, mitochondrial dysfunction, sperm DNA damage, endoplasmic reticulum stress, apoptosis and autophagy of testicular cells, repressed expression of steroidogenic enzymes and steroidogenic acute regulatory protein, disrupted hypothalamic-pituitary-testicular (HPT) axis, and gut microbiota alteration. These KEs further induced the reduction of testosterone, impaired blood-testis barrier (BTB), testicular inflammation, and impaired spermatogenesis at tissue/organ levels. Ultimately, decreased sperm quality or quantity was noted and proved by meta-analysis, which demonstrated that MPs/NPs led to a decrease of 5.99 million/mL in sperm concentration, 14.62% in sperm motility, and 23.56% in sperm viability, while causing an increase of 10.65% in sperm abnormality rate. Overall, this is the first AOP for MPs/NPs-mediated male reproductive toxicity in mammals. The innovative integration of meta-analysis into the AOP analysis increases the rigorism of the results.

Understanding microplastic pollution: Tracing the footprints and eco-friendly solutions

Microplastics (MPs) pollution has emerged as a critical environmental issue with far-reaching consequences for ecosystems and human health. These are plastic particles measuring <5 mm and are categorized as primary and secondary based on their origin. Primary MPs are used in various products like cosmetics, scrubs, body wash, and toothpaste, while secondary MPs are generated through the degradation of plastic products. These have been detected in seas, rivers, snow, indoor air, and seafood, posing potential risks to human health through the food chain. Detecting and quantifying MPs are essential to understand their distribution and abundance in the environment. Various microscopic (fluorescence microscopy, scanning electron microscopy) and spectroscopy techniques (FTIR, Raman spectroscopy, X-ray photoelectron spectroscopy) have been reported to analyse MPs. Despite the challenges in scalable removal methods, biological systems have emerged as promising options for eco-friendly MPs remediation. Algae, bacteria, and fungi have shown the potential to adsorb and degrade MPs in wastewater treatment plants (WWTPs) offering hope for mitigating this global crisis. This review examines the sources, impacts, detection, and biological removal of MPs, highlighting future directions in this crucial field of environmental conservation. By fostering global collaboration and innovative research a path towards a cleaner and healthier planet for future generations can be promised.

Chronic exposure to polystyrene microplastics increased the chemosensitivity of normal human liver cells via ABC transporter inhibition

Microplastics (MPs) are ubiquitous in environmental compartments and consumer products. Although liver is frequently reported to be a target organ of MP accumulation in mammals, few studies have focused on MP hepatoxicity in humans. In this study, we used normal human liver cells, THLE-2, to assess the acute and chronic toxicity of polystyrene (PS) MPs with sizes of 0.1 and 1 μm. The results showed that after 48 h of exposure, both kinds of PS MPs could enter THLE-2 cells and cause no obviously acute cytotoxicity at <20 μg/mL. In contrast, metabolomic analysis revealed that 90 days of PS MPs exposure at environmentally relevant dose (0.2 μg/mL) could significantly alter the metabolic profiles of the cells, especially the nanosized MPs. KEGG pathway analysis showed that the ATP-binding cassette (ABC) transporter pathway was the most significantly changed pathway. Cell functional tests confirmed that chronic PS MP treatment could inhibit the activity of the ABC efflux transporter and further increase the cytotoxicity of arsenic, indicating that the PS MPs had a chemosensitizing effect. These findings underline the chronic risk of MPs to human liver.

Melatonin alleviates oxidative stress damage in mouse testes induced by bisphenol A

We investigated the effect of melatonin on bisphenol A (BPA)-induced oxidative stress damage in testicular tissue and Leydig cells. Mice were gavaged with 50 mg/kg BPA for 30 days, and concurrently, were injected with melatonin (10 mg/kg and 20 mg/kg). Leydig cells were treated with 10 μmol/L of BPA and melatonin. The morphology and organ index of the testis and epididymis were observed and calculated. The sperm viability and density were determined. The expressions of melatonin receptor 1A and luteinizing hormone receptor, and the levels of malonaldehyde, antioxidant enzymes, glutathione, steroid hormone synthases, aromatase, luteinizing hormone, testosterone, and estradiol were measured. TUNEL assay was utilized to detect testicular cell apoptosis. The administration of melatonin at 20 mg/kg significantly improved the testicular index and epididymis index in mice treated with BPA. Additionally, melatonin promoted the development of seminiferous tubules in the testes. Furthermore, the treatment with 20 mg/kg melatonin significantly increased sperm viability and sperm density in mice, while also promoting the expressions of melatonin receptor 1A and luteinizing hormone receptor in Leydig cells of BPA-treated mice. Significantly, melatonin reduced the level of malonaldehyde in testicular tissue and increased the expression of antioxidant enzymes (superoxide dismutase 1, superoxide dismutase 2, and catalase) as well as the content of glutathione. Moreover, melatonin also reduced the number of apoptotic Leydig cells and spermatogonia, aromatase expression, and estradiol level, while increasing the expression of steroid hormone synthases (steroidogenic acute regulatory protein, cytochrome P450 family 17a1, cytochrome P450 17α-hydroxylase/20-lyase, and, 17β-hydroxysteroid dehydrogenase) and the level of testosterone. Melatonin exhibited significant potential in alleviating testicular oxidative stress damage caused by BPA. These beneficial effects may be attributed to melatonin's ability to enhance the antioxidant capacity of testicular tissue, promote testosterone synthesis, and reduce testicular cell apoptosis.

Integrated cell metabolomics and network pharmacology approach deciphers the anti-testosterone deficiency mechanisms of Bushen Zhuanggu Tang

Testicular dysfunction is distinguished by a deficiency in testosterone levels, which can be attributed to the occurrence of oxidative stress injury in Leydig cells. The empirical prescription known as Bushen Zhuanggu Tang, developed by a highly experienced traditional Chinese medicine practitioner with six decades of clinical expertize, aligns with the traditional Chinese medicine principle of "kidney governing bone". Researchers have demonstrated that the administration of BSZGT can effectively enhance testosterone production. The objective of this study is to investigate the potential anti-testicular dysfunction effects of BSZGT and elucidate its underlying mechanism in an in vitro setting. Specifically, the impact of oxidative stress induced by H2O2 on the activity and testosterone levels of Leydig cells (TM3) was examined. Furthermore, the utilization of UPLC-QE-Qrbitrap-MS enabled the identification of the involvement of BSZGT in various metabolic pathways, including arginine biosynthesis, amino acyl-tRNA biosynthesis, Alanine, aspartate and glutamine metabolism, and Citrate Cycle, through the modulation of 25 distinct metabolites. Additionally, a network pharmacological analysis was conducted to investigate the pivotal protein targets associated with the therapeutic effects of BSZGT. The findings demonstrate the identification of six key proteins (CYP19A1, CYP1B1, ALOX5, ARG1, XDH, and MPO) that play a significant role in augmenting testicular function through their involvement in the ovarian steroid production pathway. In summary, our study presents a comprehensive research methodology that combines cell metabonomics and network pharmacology to enhance the discovery of new therapeutic agents for TD.

Effects of combined exposure to polystyrene microplastics and 17α-Methyltestosterone on the reproductive system of zebrafish

Polystyrene microplastics (PS-MPs) are important carriers of pollutants in water. 17α-Methyltestosterone (MT) is a synthetic environmental endocrine disrupting chemical (EDC) with androgenic effects. To study the effects of PS-MPs and MT on zebrafish reproductive systems, zebrafish were exposed to 0 or 50 ng L-1 MT, 0.5 mg∙L-1 PS-MPs, or 50 ng∙L-1 MT + 0.5 mg∙L-1 PS-MPs for 21 d. The results showed that the different exposure reagents caused varying degrees of damage to the reproductive systems in zebrafish, with the extent of damage increasing as the exposure duration increased. Histological analysis of the gonads revealed that the ratio of mature oocytes and mature spermatozoa in the gonad decreased gradually with increased exposure time, with the ratio being Control > PS-MPs > MT > MT + PS-MPs in decreasing order. The results of quantitative real-time PCR (qRT‒PCR) showed that in female fish treated for 7 d, the expression of cyp11a mRNA was significantly reduced in all three treatment groups(MT, PS-MPs, and MT + PS-MPs), while in the group treated for 14 d with MT + PS-MPs, the expression of cyp19a1a and StAR mRNA was significantly increased. In male fish exposed for 21 d, the expression of cyp11a, cyp17a1, cyp19a1a, StAR, 3β-HSD, and 17β-HSD3 mRNA was significantly decreased in MT + PS-MPs. ELISA results showed that after 14 d of exposure, the levels of E2, LH, and FSH in the ovaries of female fish were significantly reduced in all three treatment groups. Similarly, the levels of T, E2, LH, and FSH in the testis of male fish were significantly reduced after 14 d of exposure to PS-MPs and MT + PS-MPs. Offspring of zebrafish exposed to MT and MT + PS-MPs exhibited delayed incubation time and slow development. The cross-generational toxicity of PS-MPs themselves may be negligible, but it can exacerbate the toxicity of MT, making the cross-generational effects more pronounced in the offspring, causing offspring mortality and malformations. Offspring of zebrafish exposed to MT and MT + PS-MPs exhibited delayed incubation time and slow development. In addition, MT caused malformations such as pericardial edema, yolk cysts, and spinal deformities in zebrafish during the incubation period.

Shape- and polymer-considered simulation to unravel the estuarine microplastics fate

Environmental microplastics (MPs) constitute various sizes, polymers, and shape components. In estuaries, such differences are related to the reliability of assessing the seaward fate of MPs, aggregation hotspots, and ecological risks. This study sets the MP particle mass gradient using the shape factor and size probability density function to categorically estimate the MP load in the surface layer of the Yangtze River Estuary (YRE), which is the largest contributor of plastics to the sea. During the high plastic input period in July, the optimized estimated MP load through the surface layer of the YRE was 9766 kg/month, which was overestimated by 821 kg/month based on the empirical average particle mass. While tracking MP transport classified by shape and polymer type, the resuspension of MPs that accumulate in the intertidal zone cannot be neglected. The average relative error of the simulation was as low as 19.6% after including the abovementioned factors. Finally, the simulation results of the sensitive regions were extracted to assess the new MP risk index, which considers shape, abundance, and polymer type. By introducing these essential tools, this study helps to understand the fate of riverine MPs entering estuaries, where valuable opportunities for removing MPs exist before they spread to the oceans.