The detrimental effects of micro-and nano-plastics on digestive system: An overview of oxidative stress-related adverse outcome pathway

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

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

Nickel-based nanomaterials: a comprehensive analysis of risk assessment, toxicity mechanisms, and future strategies for health risk prevention

Nickel-based nanomaterials (NBNs) have seen a surge in usage across a variety of applications. However, the widespread use of NBNs has led to increased human exposure, raising questions about their associated health risks, both in the short and long term. Additionally, the spread of NBNs in the environment has attracted considerable attention, emerging as a vital focus for research and development. This review aims to provide an in-depth assessment of the current understanding of NBNs toxicity, the mechanisms underlying their toxicological effects, and the strategies for mitigating associated health risks. We begin by examining the physicochemical properties of NBNs, such as particle size, composition and surface functionalization, which are key determinants of their biological interactions and toxicity. Then, through an extensive analysis of in vitro and in vivo studies, we highlight the adverse effects of NBNs exposure, including the generation of reactive oxygen species (ROS), oxidative stress, inflammation, cytotoxicity, genotoxicity, and immunotoxicity. To address the potential health risks associated with NBNs, we propose future strategies for risk prevention, including the development of safer nanomaterial designs, implementation of stringent regulatory guidelines, and advancement of novel toxicity testing approaches.

Micro- and Nano-Plastic-Induced Adverse Health Effects on Lungs and Kidneys Linked to Oxidative Stress and Inflammation

Micro- and nano-plastics (MNPs) are small plastic particles that result from the breakdown of larger plastics. They are widely dispersed in the environment and pose a threat to wildlife and humans. MNPs are present in almost all everyday items, including food, drinks, and household products. Air inhalation can also lead to exposure to MNPs. Research in animals indicates that once MNPs are absorbed, they can spread to various organs, including the liver, spleen, heart, lungs, thymus, reproductive organs, kidneys, and even the brain by crossing the blood-brain barrier. Furthermore, MPs can transport persistent organic pollutants or heavy metals from invertebrates to higher levels in the food chain. When ingested, the additives and monomers that comprise MNPs can disrupt essential biological processes in the human body, thereby leading to disturbances in the endocrine and immune systems. During the 2019 coronavirus (COVID-19) pandemic, there was a significant increase in the global use of polypropylene-based face masks, leading to insufficient waste management and exacerbating plastic pollution. This review examines the existing research on the impact of MNP inhalation on human lung and kidney health based on in vitro and in vivo studies. Over the past decades, a wide range of studies suggest that MNPs can impact both lung and kidney tissues under both healthy and diseased conditions. Therefore, this review emphasizes the need for additional studies employing multi-approach analyses of various associated biomarkers and mechanisms to gain a comprehensive and precise understanding of the impact of MNPs on human health.

The FOXO pathway mediates a conserved mechanism of antioxidant defense against microplastic-induced toxicity in Aurelia coerulea polyps and mouse liver

Microplastics are emerging as a critical class of pollutants with a pervasive presence in the atmosphere, oceans, and terrestrial environments, raising global concern. However, it is unclear whether there are conserved mechanisms for the response of microplastic damage to different species. Aurelia coerulea polyps and mouse models were exposed to microplastic environments to assess their growth effects and mechanisms. The similarities and differences in the defence mechanisms of the two species after exposure to microplastics were analysed by means of phenotypic observations, transcriptome sequencing, pathological sections, oxidative stress indicators, explosions and molecular docking. Exposure to 200 mg/L of PS-MPs resulted in morphological changes, tissue damage, and oxidative stress in polyps. Exposure to 600 mg/L of PS-MPs led to increased toxicity in the mouse liver, including rupture and apoptosis of mitochondria and nuclei in hepatocytes, as well as oxidative stress. Meanwhile, we found that their antioxidant defense and DNA damage repair pathways were significantly altered. In addition, we found that the same loci existed in the foxo pathway in both species, and the enriched gene sequences were 48.33 % similar. Molecular docking showed conserved regions between polyps NLK and mouse Mapk13, indicating similar kinase activities, but overall structural and functional differences suggest species-specific. This finding provide new insights into understanding the mechanisms of toxicity of MPs to different organisms.

NiO/AgNPs nanowell enhanced SERS sensor for efficient detection of micro/nanoplastics in beverages

The ubiquity of plastic products has led to an increased exposure to micro and nano plastics across diverse environments, presenting a novel class of pollutants with substantial health implications. Emerging research indicates their capacity to infiltrate human organs, posing risks of tissue damage and carcinogenesis. Given the prevalent consumption of beverages as a primary vector for these plastics' entry into the human system, there is an imperative need for the advancement of precise detection methodologies in liquids. In this study, we introduce a substrate comprising a Nickel Oxide (NiO) nanosheet array decorated with Silver Nanoparticles (AgNPs) for the Surface-Enhanced Raman Spectroscopy (SERS) analysis of micro//nano plastics. This configuration, leveraging a unique nanowell architecture alongside silver plasmonic enhancement, demonstrates unparalleled sensitivity and repeatability in signal, facilitating the accurate quantification of these contaminants. Through the application of a portable Raman apparatus, this study successfully identifies prevalent micro/nano plastics including polystyrene (PS), polyethylene (PE), and polypropylene (PP), achieving detection sensitivities of 5 μg/mL, 25 μg/mL, and 25 μg/mL, respectively. Moreover, the substrate's efficacy extends to the detection of PS within commonly consumed beverages such as water, milk, and liquor with sensitivities of 25 μg/mL, 50 μg/mL, and 50 μg/mL, respectively. These findings highlight the substrate's potential as an expedient and effective sensor for the real-time monitoring of micro/nano plastic pollutants.

What if you eat nanoplastics? Simulating nanoplastics fate during gastrointestinal digestion

Despite our growing awareness of micro-and nanoplastics presence in food and beverages, the fate of nanoplastics (NPs) in the human gastrointestinal tract (GIT) remains poorly investigated. Changes of nanoplastics size upon digestive conditions influence the potential of absorption through the intestine. In this study, polymer nanoparticles with different physicochemical properties (size, surface and chemistry) were submitted to gastrointestinal digestion (GID) simulated in vitro. Their agglomeration behaviour was measured with a unique set of analytical approaches, allowing to study NPs' interactions with the digestive enzymes. Smaller NPs agglomerated more, narrowing the overall particle size distribution of smaller and larger NPs. NPs of different polymers exhibited heteroagglomeration. Digestive enzymes interact with the NPs, forming large but fragile agglomerates. In presence of the enzymes, even acid-functionalized NPs, typically stable in harsh conditions, agglomerated similarly to the non-functionalized PS NPs. These results highlight the role of the GID in increasing the effective size of ingested NPs, potentially reducing their ability to pass through the cell membranes. Our findings address a critical knowledge gap in nanoplastics oral uptake potential, providing a solid technical foundation for their characterization.

Nanoplastic-Induced Liver Damage Was Alleviated by Maltol via Enhancing Autophagic Flow: An In Vivo and In Vitro Study

In recent years, there has been a growing concern regarding health issues arising from exposure to nanoplastics (Nps) in the natural environment. The Nps bioaccumulate within the body via the circulatory system and accumulate in the liver, resulting in damage. Previous studies have demonstrated that maltol, derived from red ginseng (Panax ginseng C.A. Meyer) as a Maillard product, exhibits hepatoprotective effects by alleviating liver damage caused by carbon tetrachloride or cisplatin. In order to explore the specific mechanism of maltol in improving hepatotoxicity induced by Nps, mice exposed to 100 mg/kg Nps were given maltol at doses of 50 and 100 mg/kg, respectively. The results showed that Nps induced an increase in the levels of liver apoptotic factors BAX and cytochrome c, a decrease in the levels of the autophagy key gene LC3 II/I, and an increase in P62. It also caused oxidative stress by affecting the Nrf2/HO-1 pathway, and a decrease in GPX4 protein expression suggested the occurrence of ferroptosis. However, treatment with maltol significantly improved these changes. In addition, maltol (2, 4, and 8 μM) also protected human normal liver L02 cells from Np (400 μg/mL)-induced damage. Our data suggest that maltol could ameliorate Np-induced L02 cytotoxicity by reducing autophagy-dependent oxidative stress, exhibiting similar protective effects in vitro as in vivo. This study helps shed light on the specific molecular mechanism of Np-induced hepatotoxicity. For the first time, we studied the protective effect of maltol on Np-induced liver injury from multiple perspectives, expanding the possibility of treatment for diseases caused by environmental pollutants.

Health effects of microplastics and nanoplastics: review of published case reports

Microplastics and nanoplastics (MNPs) represent a pervasive environmental pollutant, raising significant concerns about potential health effects on humans. These tiny plastic particles have been detected across various environmental matrices, including air, water, soil, and food sources. While the adverse impacts of MNPs on wildlife and ecosystems are well-documented, understanding their effects on human health is still in its infancy. This study aims to comprehensively review existing case reports documenting adverse health outcomes associated with MNPs exposure. Through an extensive literature search, relevant articles were identified and analyzed. MNPs exposure primarily occurs through ingestion and inhalation routes. Health effects on the digestive system include oxidative stress, inflammation, dysbiosis, and metabolic disorders, with cases linking MNPs exposure to gastrointestinal injury and liver dysfunction. Respiratory system impacts include asthma exacerbation and hypersensitivity pneumonitis, particularly in industries involving plastic production. MNPs exposure has also been associated with nervous system conditions, reproductive toxicity, skeletal system interference, excretory system disruption, and cardiovascular morbidity and mortality. Despite limited case reports, the widespread presence of MNPs warrants further investigation into their potential health risks. This study underscores the urgency of understanding and mitigating the adverse health effects posed by MNPs exposure. Further research is imperative in order to comprehensively assess and address the dangers associated with MNPs contamination in the environment.

Microplastics and Oxidative Stress-Current Problems and Prospects

Microplastics (MPs) are plastic particles between 0.1 and 5000 µm in size that have attracted considerable attention from the scientific community and the general public, as they threaten the environment. Microplastics contribute to various harmful effects, including lipid peroxidation, DNA damage, activation of mitogen-activated protein kinase pathways, cell membrane breakages, mitochondrial dysfunction, lysosomal defects, inflammation, and apoptosis. They affect cells, tissues, organs, and overall health, potentially contributing to conditions like cancer and cardiovascular disease. They pose a significant danger due to their widespread occurrence in food. In recent years, information has emerged indicating that MPs can cause oxidative stress (OS), a known factor in accelerating the aging of organisms. This comprehensive evaluation exposed notable variability in the reported connection between MPs and OS. This work aims to provide a critical review of whether the harmfulness of plastic particles that constitute environmental contaminants may result from OS through a comprehensive analysis of recent research and existing scientific literature, as well as an assessment of the characteristics of MPs causing OS. Additionally, the article covers the analytical methodology used in this field. The conclusions of this review point to the necessity for further research into the effects of MPs on OS.

Unraveling Intracellular Protein Corona Components of Nanoplastics via Photocatalytic Protein Proximity Labeling

Bioaccumulation of nanoplastic particles has drawn increasing attention regarding environmental sustainability and biosafety. How nanoplastic particles interact with the cellular milieu still remains elusive. Herein, we exemplify a general approach to profile the composition of a "protein corona" interacting with nanoparticles via the photocatalytic protein proximity labeling method. To enable photocatalytic proximity labeling of the proteome interacting with particles, iodine-substituted BODIPY (I-BODIPY) is selected as the photosensitizer and covalently conjugated onto amino-polystyrene nanoparticles as a model system. Next, selective proximity labeling of interacting proteins is demonstrated using I-BODIPY-labeled nanoplastic particles in both Escherichia coli lysate and live alpha mouse liver 12 cells. Mechanistic studies reveal that the covalent modifications of proteins by an aminoalkyne substrate are conducted via a reactive oxygen species photosensitization pathway. Further proteomic analysis uncovers that mitochondria-related proteins are intensively involved in the protein corona, indicating substantial interactions between nanoplastic particles and mitochondria. In addition, proteostasis network components are also identified, accompanied by consequent cellular proteome aggregation confirmed by fluorescence imaging. Together, this work exemplifies a general strategy to interrogate the composition of the protein corona of nanomaterials by endowing them with photooxidation properties to enable photocatalytic protein proximity labeling function.

Differences in toxicity induced by the various polymer types of nanoplastics on HepG2 cells

The problem of microplastics (MPs) contamination in food has gradually come to the fore. MPs can be transmitted through the food chain and accumulate within various organisms, ultimately posing a threat to human health. The concentration of nanoplastics (NPs) exposed to humans may be higher than that of MPs. For the first time, we studied the differences in toxicity, and potential toxic effects of different polymer types of NPs, namely, polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polystyrene (PS) on HepG2 cells. In this study, PET-NPs, PVC-NPs, and PS-NPs, which had similar particle size, surface charge, and shape, were prepared using nanoprecipitation and emulsion polymerization. The results of the CCK-8 assay showed that the PET-NPs and PVC-NPs induced a decrease in cell viability in a concentration-dependent manner, and their lowest concentrations causing significant cytotoxicity were 100 and 150 μg/mL, respectively. Moreover, the major cytotoxic effects of PET-NPs and PVC-NPs at high concentrations may be to induce an increase in intracellular ROS, which in turn induces cellular damage and other toxic effects. Notably, our study suggested that PET-NPs and PVC-NPs may induce apoptosis in HepG2 cells through the mitochondrial apoptotic pathway. However, no relevant cytotoxicity, oxidative damage, and apoptotic toxic effects were detected in HepG2 cells with exposure to PS-NPs. Furthermore, the analysis of transcriptomics data suggested that PET-NPs and PVC-NPs could significantly inhibit the expression of DNA repair-related genes in the p53 signaling pathway. Compared to PS-NPs, the expression levels of lipid metabolism-related genes were down-regulated to a greater extent by PET-NPs and PVC-NPs. In conclusion, PET-NPs and PVC-NPs were able to induce higher cytotoxic effects than PS-NPs, in which the density and chemical structure of NPs of different polymer types may be the key factors causing the differences in toxicity.

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.

Polystyrene micro- and nanoplastics induce gastric toxicity through ROS mediated oxidative stress and P62/Keap1/Nrf2 pathway

Microplastics (MPs) exist widely in the environment and can enter the human body indirectly through the food chain or directly through inhalation or ingestion. The primary organ that MPs contaminated food or water enters the human body through the digestive tract is the stomach. However, at present, the effects of MPs on the stomach and the related mechanism remain unclear. In this study, our results indicated that 50 nm and 250 nm polystyrene MPs (PS-MPs) at environmental related dose significantly decreased stomach organ coefficient, inhibited gastric juice secretion and mucus secretion, disrupted gastric barrier function and suppressed antioxidant ability in mice. In vitro experiments showed that PS-MPs inhibited cell viability, increased ROS generation, and induced apoptosis through mitochondria-dependent pathway. Simultaneously, PS-MPs also decreased mitochondrial membrane potential, ATP level, disrupted mitochondrial kinetic homeostasis, and activated P62 / Nrf2 / Keap1 pathway. Furthermore, blocking ROS (NAC) partially alleviated ROS and apoptosis caused by PS-MPs. Based on above findings, the potential adverse outcome pathway (AOP) of PS-MPs-caused gastric toxicity was proposed which provides a new insight into the risk assessment of MP related gastric damage. Our study unveils the gastric injury induced by PS MPs is dependent on ROS - mediated P62 / Nrf2 / Keap1 signaling pathway, and provides scientific basis for further exploration the mechanism of gastric toxicity of PS MPs.

Size-dependent toxicity of polystyrene microplastics on the gastrointestinal tract: Oxidative stress related-DNA damage and potential carcinogenicity

Microplastics (MPs) and nanoplastics (NPs) have been generally regarded as emerging pollutants and received worldwide attention in recent years. Water and food consumption are the primary pathways for human exposure to MPs/NPs, thus gastrointestinal tracts may be susceptible to their toxicity. Although the recent report has indicated the presence of MPs/NPs in multiple human organs, little is known about their gastric effects. Therefore, this study focused on the adverse effects of polystyrene microplastics (PS-MPs) on gastric epithelium in vivo and in vitro. Surface-enhanced Raman spectroscopy (SERS) revealed the distribution of PS-MPs was associated with their particle sizes, and predominantly concentrated in gastric tissues. Gastric barrier injury and mitochondrial damage were observed in rats after exposure to PS-MPs. Compared with the larger ones, polystyrene nanoplastics (PS-NPs) more significantly reduced the activity of antioxidant enzymes while enhancing the level of MDA, 8-OhdG and γ-H2AX. Meanwhile, PS-MPs caused upregulation of β-catenin/YAP through redox-dependent regulation of nucleoredoxin (NXN) and dishevelled (Dvl). These findings supported the size-dependent effects of PS-MPs on oxidative stress and DNA damage. Moreover, the redox-dependent activation of the β-catenin/YAP cascade suggested a novel toxic mechanism for PS-MPs and implied the potential carcinogenic effects.

A comprehensive review on the source, ingestion route, attachment and toxicity of microplastics/nanoplastics in human systems

Microplastics (MPs)/nanoplastics (NPs) are widely found in the natural environment, including soil, water and the atmosphere, which are essential for human survival. In the recent years, there has been a growing concern about the potential impact of MPs/NPs on human health. Due to the increasing interest in this research and the limited number of studies related to the health effects of MPs/NPs on humans, it is necessary to conduct a systematic assessment and review of their potentially toxic effects on human organs and tissues. Humans can be exposed to microplastics through ingestion, inhalation and dermal contact, however, ingestion and inhalation are considered as the primary routes. The ingested MPs/NPs mainly consist of plastic particles with a particle size ranging from 0.1 to 1 μm, that distribute across various tissues and organs within the body, which in turn have a certain impact on the nine major systems of the human body, especially the digestive system and respiratory system, which are closely related to the intake pathway of MPs/NPs. The harmful effects caused by MPs/NPs primarily occur through potential toxic mechanisms such as induction of oxidative stress, generation of inflammatory responses, alteration of lipid metabolism or energy metabolism or expression of related functional factors. This review can help people to systematically understand the hazards of MPs/NPs and related toxicity mechanisms from the level of nine biological systems. It allows MPs/NPs pollution to be emphasized, and it is also hoped that research on their toxic effects will be strengthened in the future.

Non-traditional species sensitivity distribution approaches to analyze hazardous concentrations of microplastics in marine water

Owing to their ubiquitous nature, microplastics are a major environmental concern. This study reviewed the toxicity data of microplastics in marine water, and analyzed their species sensitivity distribution (SSD) curves and hazardous concentrations (HCs). Toxicity database of no-observed effect concentration (NOEC), 50% effect concentration (EC50), and highest observed no-effect concentration (HONEC), and lethal, developing, reproductive, biochemical, and behavioral toxicity endpoints was used. Using 169 chronic NOEC databases, all non-traditional toxicity endpoint databases showed stronger HC values, better fit, and more variable toxicity sensitivity than those derived from traditional values. Moreover, using 426 chronic NOEC, EC50, and HONEC data points, HC values calculated from traditional plus HONEC toxicity values showed weaker HC values, slightly better fit, and more variable toxicity sensitivity than those derived from traditional toxicity values. The SSD approach using non-traditional toxicity and marine water toxicity data can expand the marine water toxicity database, including information on SSD curves and HCs of diverse microplastics.

Determining the Contribution of Micro/Nanoplastics to Antimicrobial Resistance: Challenges and Perspectives

Microorganisms colonizing the surfaces of microplastics form a plastisphere in the environment, which captures miscellaneous substances. The plastisphere, owning to its inherently complex nature, may serve as a "Petri dish" for the development and dissemination of antibiotic resistance genes (ARGs), adding a layer of complexity in tackling the global challenge of both microplastics and ARGs. Increasing studies have drawn insights into the extent to which the proliferation of ARGs occurred in the presence of micro/nanoplastics, thereby increasing antimicrobial resistance (AMR). However, a comprehensive review is still lacking in consideration of the current increasingly scattered research focus and results. This review focuses on the spread of ARGs mediated by microplastics, especially on the challenges and perspectives on determining the contribution of microplastics to AMR. The plastisphere accumulates biotic and abiotic materials on the persistent surfaces, which, in turn, offers a preferred environment for gene exchange within and across the boundary of the plastisphere. Microplastics breaking down to smaller sizes, such as nanoscale, can possibly promote the horizontal gene transfer of ARGs as environmental stressors by inducing the overgeneration of reactive oxygen species. Additionally, we also discussed methods, especially quantitatively comparing ARG profiles among different environmental samples in this emerging field and the challenges that multidimensional parameters are in great necessity to systematically determine the antimicrobial dissemination risk in the plastisphere. Finally, based on the biological sequencing data, we offered a framework to assess the AMR risks of micro/nanoplastics and biocolonizable microparticles that leverage multidimensional AMR-associated messages, including the ARGs' abundance, mobility, and potential acquisition by pathogens.