Polyvinyl chloride microplastics induce changes in gene expression and organ histology along the HPG axis in Cyprinus carpio var. larvae

Plastics and their derivatives are impacting animal ecophysiology: A review

Nowadays, plastic pollution is one of the most significant issues affecting the environment, posing a serious threat to marine biodiversity, ecosystem stability, and human health. Millions of tons of plastic waste enter the oceans every year, and the impact of microplastics (MPs) is much more worrying than visible contamination. The presence of these particles puts a strain on ecological dynamics, causing a significant impact on the health of marine organisms and affects humans due to the interconnection existing with the environment and the food chain. This review article examines the different ways in which MPs interact with marine life, the mechanisms that drive this pollution, and the cascading consequences for the health of organisms and ecosystems. It also highlights the critical links between plastic pollution and human health and underlines the urgency of a global and coordinated approach to address this growing crisis. Only through deeper understanding, increased awareness and collective action can we hope to mitigate the significant impacts of plastic pollution and ensure a sustainable future for oceans and our planet.

Long-term effects of individual and combined exposure to microplastics and copper in zebrafish hypothalamic-pituitary-gonadal axis - A multi-biomarker evaluation

Microplastics (MPs) pollution and metal contamination are two prominent environmental stressors with multifaceted implications for aquatic life and ecosystem health. However, the underlying toxicological mechanisms of MPs and metals co-exposure on fish reproduction processes are largely unknown. In this study, zebrafish (Danio rerio) were exposed to MPs (2 mg/L), copper (25 μg/L, Cu25), and their mixture (Cu25 + MPs), for 30 days. The oxidative stress response, along with the expression profile of the hypothalamic-pituitary-gonadal (HPG) axis-related genes in the brain and gonad of zebrafish, were evaluated. The findings demonstrated that exposure to MPs and Cu affects the antioxidant system of zebrafish brain and gonads, inhibiting GPx in individuals exposed to MPs, Cu25, and their mixture. The gene expression analysis revealed dysregulation of the HPG axis-related genes. Specifically, the androgen receptor (ar), estrogen receptor 1 (esr1), follicle-stimulating hormone (fsh), and gonadotropin-releasing hormone 2 (gnrh2) were upregulated in the brain, whereas the genes esr2a, ar, cytochrome P450 family 11 subfamily A member 1 (cyp11a) and cyp19a were upregulated in the gonads. Both the biochemical and gene expression results showed that the brain and gonads were differently affected by MPs and Cu with the effects varying with fish gender. Furthermore, the mixture exposure affected the brain the most, and the individual pollutants affected the gonads the most. Overall, this study highlights that MPs, alone or combined with Cu, adversely affect the HPG axis of zebrafish, posing a potential threat to the reproduction of fish populations.

Global distribution characteristics and ecological risk assessment of microplastics in aquatic organisms based on meta-analysis

As microplastic pollution in the natural environment intensifies, the risk of microplastic contamination faced by aquatic organisms has garnered increasing widespread attention. Most studies have primarily focused on the impacts of microplastics within specific regions and on particular species. However, with the global migration of microplastics, it is necessary to conduct comprehensive research on the distribution characteristics, ingestion mechanisms, and ecological impacts of microplastics across various aquatic organisms. To address this research gap, the present study systematically evaluates the distribution status of microplastics in global aquatic organisms and assesses their potential ecological risks. Firstly, a review of the sources and impacts of microplastics within aquatic organisms is provided. Secondly, a bibliometric analysis is employed to examine the current research landscape and trends, coupled with a quantitative analysis of how the biological characteristics of aquatic organisms influence microplastic ingestion and the distribution patterns of microplastics within these organisms. Thirdly, the study investigates the mechanisms by which microplastics affect aquatic food chains by examining their impact on organisms at different trophic levels. Finally, strategies to reduce microplastic input into water bodies and future research directions are proposed. The findings offer scientific foundations and decision-making support for global microplastic pollution control, aiming to protect the health and sustainable development of aquatic ecosystems.

Biotransport and toxic effects of micro- and nanoplastics in fish model and their potential risk to humans: A review

The growing body of scientific evidence suggests that micro- and nanoplastics (MPs/NPs) pose a significant threat to aquatic ecosystems and human health. These particles can enter organisms through ingestion, inhalation, dermal contact, and trophic transfer. Exposure can directly affect multiple organs and systems (respiratory, digestive, neurological, reproductive, urinary, cardiovascular) and activate extensive intracellular signaling, inducing cytotoxicity involving mechanisms such as membrane disruption, extracellular polymer degradation, reactive oxygen species (ROS) production, DNA damage, cellular pore blockage, lysosomal instability, and mitochondrial depolarization. This review focuses on current research examining the in vivo and in vitro toxic effects of MPs/NPs on aquatic organisms, particularly fish, in relation to particulate toxicity aspects (such as particle transport mechanisms and structural modifications). Meanwhile, from the perspectives of the food chain and environmental factors, it emphasizes the comprehensive threats of MPs/NPs to human health in terms of both direct and indirect toxicity. Additionally, future research needs and strategies are discussed to aid in mitigating the potential risks of particulate plastics as carriers of toxic trace elements to human health.

Mercuric chloride induced reproductive toxicity associated with oxidative damage in male Wistar albino rat, Rattus norvegicus

In the field of toxicology, male reproductive hazards attributed to metal exposure is a fast-developing issue. Mercury has been identified as an environmental pollutant that causes potential adverse impacts on organisms. This study aimed to assess the reprotoxic consequences of mercuric chloride (HgCl2). Five groups of sexually mature albino rats were given oral mercuric chloride (HgCl2) treatment. (G1) control group received saline treatment; (G2) (5.25 mg/kg of HgCl2 for 30 days); (G3) (5.25 mg/kg of HgCl2 for 60 days); (G4) (10.5 mg/kg of HgCl2 for 30 days); (G5) (10.5 mg/kg of HgCl2 for 60 days). The hormonal levels, sperm count, sperm motility, sperm viability, and reproductive organ weight, including body weight, were substantially reduced, whereas the sperm abnormality rate was enhanced in rat groups treated with HgCl2. The analysis revealed that the effect size (Cohen's d) for sperm parameters, including sperm count, motility and viability, were extremely high across all groups, except for sperm abnormality in group 2 (d = 0.59) and group 3 (d = 0.18), where moderate and small effect sizes were observed respectively, and this suggests a significant impact of the intervention on sperm parameters. The administration of HgCl2 resulted in the induction of oxidative stress in testis that is manifested by substantially enhanced lipid peroxidation (MDA) with a substantial decrease in activity of antioxidant enzymes like catalase (CAT), superoxide dismutase (SOD), reduced glutathione (GSH), and glutathione peroxidase (GPx) in testes of mercury-treated groups. Concomitantly, there was downregulation in the mRNA levels of the genes involved in spermatogenesis, namely Hsp-70, insulin-like growth factor (IGF), glutathione-S-transferase, and p53 in the testis. The expression of antiapoptotic protein B cell lymphoma (Bcl-2) was decreased, and conversely, the expression of cell proliferative protein Ki-67 was increased in a dose- and duration-dependent manner. Histopathological studies showed degenerative changes in the testis, epididymis, prostate gland, and seminal vesicle, compared to the control group. All the evidence suggests that after mercury exposure, there may be an imbalance between the body's defenses against free radicals and antioxidants, making the testis more susceptible to oxidative damage. This imbalance could potentially have a detrimental effect on the function of the male reproductive system.

Revisiting cadmium-induced toxicity in the male reproductive system: an update

Heavy metals like cadmium (Cd) are one of the main environmental pollutants, with no biological role in the human body. Cd has been well-documented to have disastrous effects on both plants and animals. It is known to accumulate in kidneys, lungs, liver, and testes and is thought to affect these organs' function over time, which is linked to a very long biological half-life and a very poor rate of elimination. According to recent researches, the testes are extremely vulnerable to cadmium. The disruption of the blood-testis barrier, seminiferous tubules, Sertoli cells, and Leydig cells caused by cadmium leads to the loss of sperm through various mechanisms, such as oxidative stress, spermatogenic cell death, testicular swelling, dysfunction in androgen-producing cells, interference with gene regulation, disruption of ionic homeostasis, and damage to the vascular endothelium. Additionally, through epigenetic control, cadmium disrupts the function of germ cells and somatic cells, resulting in infertile or subfertile males. A full grasp of the mechanisms underlying testicular toxicity caused by Cd is very important to develop suitable strategies to ameliorate male fertility. Therefore, this review article outlines cadmium's impact on growth and functions of the testicles, reviews therapeutic approaches and protective mechanisms, considers recent research findings, and identifies future research directions.

Reproductive and developmental implications of micro- and nanoplastic internalization: Recent advances and perspectives

A growing body of evidence exhibits the ubiquitous presence and accumulation of micro- and nanoplastics (MNPs) in the air, drinking water, food, and even inside the body, which has raised concerns about their potential impact on reproductive and developmental health. To comprehensively examine the current state of knowledge regarding MNPs-induced reproductive and developmental toxicity, we conducted this systematic review by focusing on the prevalence of MNPs determined in reproductive tissues and their influences on parental reproduction and offspring development. Our findings demonstrate the detection of MNPs in various human reproductive tissues, including semen, placenta, and ovarian follicular fluid, as well as in reproductive tissues of diverse animal species. We show a potential relationship between MNP exposure and increased prevalence of infertility and adverse pregnancy outcomes based on the fact that MNPs exert detrimental effects on reproductive parameters, including sperm quality, ovarian function, and steroidogenesis. In male reproductive systems, MNPs disrupt testicular tissue structure, impair reproductive endocrinology, and reduce sperm quality. In females, MNPs affect ovarian tissue structure and function, interfere with hormone secretion, and impact the endometrium and embryo implantation. Additionally, MNPs cause developmental toxicity in animal models, affecting embryonic development and offspring health, and produce transgenerational effects. Notably, in-depth literature study suggests a crucial role for oxidative stress, inflammation, and epigenetic modification in MNPs-induced toxicity. In conclusion, we integrated systematic knowledge on MNPs-induced reproductive and developmental toxicity, and the systematic finding underscores future study to fully elucidate the risks posed by MNPs to reproductive and developmental health and to inform policy decisions and public health interventions aimed at mitigating their harmful effects.

A review of the neurobehavioural, physiological, and reproductive toxicity of microplastics in fishes

Microplastics (MPs) have emerged as widespread environmental pollutants, causing significant threats to aquatic ecosystems and organisms. This review examines the toxic effects of MPs on fishes, with a focus on neurobehavioural, physiological, and reproductive impacts, as well as the underlying mechanisms of toxicity. Evidence indicates that MPs induce a range of neurobehavioural abnormalities in fishes, affecting social interactions and cognitive functions. Altered neurotransmitter levels are identified as a key mechanism driving behavioural alterations following MP exposure. Physiological abnormalities in fishes exposed to MPs are also reported, including neurotoxicity, immunotoxicity, and oxidative stress. These physiological disruptions can compromise the individual health of aquatic organisms. Furthermore, reproductive abnormalities linked to MP exposure are discussed, with a particular emphasis on disruptions in endocrine signaling pathways. These disruptions can impair reproductive success in fish species, impacting population numbers. Here we explore the critical role of endocrine disruptions in mediating reproductive effects after exposure to MPs, focusing primarily on the hypothalamic-pituitary-gonadal axis. Our review highlights the urgent need for interdisciplinary research efforts aimed at elucidating the full extent of MP toxicity and its implications for aquatic ecosystems. Lastly, we identify knowledge gaps for future research, including investigations into the transgenerational impacts, if any, of MP exposure and quantifying synergetic/antagonistic effects of MPs with other environmental pollutants. This expanded knowledge regarding the potential risks of MPs to aquatic wildlife is expected to aid policymakers in developing mitigation strategies to protect aquatic species.

Decoding the molecular concerto: Toxicotranscriptomic evaluation of microplastic and nanoplastic impacts on aquatic organisms

The pervasive and steadily increasing presence of microplastics/nanoplastics (MPs/NPs) in aquatic environments has raised significant concerns regarding their potential adverse effects on aquatic organisms and their integration into trophic dynamics. This emerging issue has garnered the attention of (eco)toxicologists, promoting the utilization of toxicotranscriptomics to unravel the responses of aquatic organisms not only to MPs/NPs but also to a wide spectrum of environmental pollutants. This review aims to systematically explore the broad repertoire of predicted molecular responses by aquatic organisms, providing valuable intuitions into complex interactions between plastic pollutants and aquatic biota. By synthesizing the latest literature, present analysis sheds light on transcriptomic signatures like gene expression, interconnected pathways and overall molecular mechanisms influenced by various plasticizers. Harmful effects of these contaminants on key genes/protein transcripts associated with crucial pathways lead to abnormal immune response, metabolic response, neural response, apoptosis and DNA damage, growth, development, reproductive abnormalities, detoxification, and oxidative stress in aquatic organisms. However, unique challenge lies in enhancing the fingerprint of MPs/NPs, presenting complicated enigma that requires decoding their specific impact at molecular levels. The exploration endeavors, not only to consolidate existing knowledge, but also to identify critical gaps in understanding, push forward the frontiers of knowledge about transcriptomic signatures of plastic contaminants. Moreover, this appraisal emphasizes the imperative to monitor and mitigate the contamination of commercially important aquatic species by MPs/NPs, highlighting the pivotal role that regulatory frameworks must play in protecting all aquatic ecosystems. This commitment aligns with the broader goal of ensuring the sustainability of aquatic resources and the resilience of ecosystems facing the growing threat of plastic pollutants.

Reproductive toxicity of cadmium stress in male animals

Cadmium (Cd) is a common heavy metal pollutant in the environment, and the widespread use of products containing Cd compounds in industry has led to excessive levels in the environment, which enter the animal body through the food chain, thus seriously affecting the reproductive development of animals. Related studies have reported that Cd severely affects spermatogonia development and spermatogenesis in animals. In contrast, the reproductive toxicity of Cd in males and its mechanism of action have not been clarified. Therefore, this paper reviewed the toxic effects of Cd on germ cells, spermatogonia somatic cells and hypothalamic-pituitary-gonadal axis (HPG axis) of male animals and its toxic action mechanisms of oxidative stress, apoptosis and autophagy from the perspectives of cytology, genetics and neuroendocrinology. The effects of Cd stress on epigenetic modification of reproductive development in male animals were also analyzed. We hope to provide a reference for the in-depth study of the toxicity of Cd on male animal reproduction.

The invisible Threat: Assessing the reproductive and transgenerational impacts of micro- and nanoplastics on fish

Micro- and nanoplastics (MNPs), emerging as pervasive environmental pollutants, present multifaceted threats to diverse ecosystems. This review critically examines the ability of MNPs to traverse biological barriers in fish, leading to their accumulation in gonadal tissues and subsequent reproductive toxicity. A focal concern is the potential transgenerational harm, where offspring not directly exposed to MNPs exhibit toxic effects. Characterized by extensive specific surface areas and marked surface hydrophobicity, MNPs readily adsorb and concentrate other environmental contaminants, potentially intensifying reproductive and transgenerational toxicity. This comprehensive analysis aims to provide profound insights into the repercussions of MNPs on fish reproductive health and progeny, highlighting the intricate interplay between MNPs and other pollutants. We delve into the mechanisms of MNPs-induced reproductive toxicity, including gonadal histopathologic alterations, oxidative stress, and disruptions in the hypothalamic-pituitary-gonadal axis. The review also underscores the urgency for future research to explore the size-specific toxic dynamics of MNPs and the long-term implications of chronic exposure. Understanding these aspects is crucial for assessing the ecological risks posed by MNPs and formulating strategies to safeguard aquatic life.