Amino-Functionalized Polystyrene Nano-Plastics Induce Mitochondria Damage in Human Umbilical Vein Endothelial Cells

Hazard assessment of nanoplastics is driven by their surface-functionalization. Effects in human-derived primary endothelial cells

During plastic waste degradation into micro/nanoplastics (MNPLs) their physicochemical characteristics including surface properties (charge, functionalization, biocorona, etc.) can change, potentially affecting their biological effects. This paper focuses on the surface functionalization of MNPLs to determine if it has a direct impact on the toxicokinetic and toxicodynamic interactions in human umbilical vein endothelial cells (HUVECs), at different exposure times. Pristine polystyrene nanoplastics (PS-NPLs), as well as their carboxylated (PS-C-NPLs) and aminated (PS-A-NPLs) forms, all around 50 nm, were used in a wide battery of toxicological assays. These assays encompassed evaluations on cell viability, cell internalization, induction of intracellular reactive oxygen species (iROS), and genotoxicity. The experiments were conducted at a concentration of 100 μg/mL, chosen to ensure a high internalization rate across all treatments while maintaining a sub-toxic concentration. Our results show that all PS-NPLs are internalized by HUVECs, but the internalization dynamic depends on the particle's functionalization. PS-NPLs and PS-C-NPLs internalization modify the morphology of the cell increasing its inner complexity/granularity. Regarding cell toxicity, only PS-A-NPLs reduced cell viability. Intracellular ROS was induced by the three different PS-NPLs but at different time points. Genotoxic damage was induced by the three PS-NPLs at short exposures (2 h), but not for PS-C-NPLs at 24 h. Overall, this study suggests that the toxicological effects of PSNPLs on HUVEC cells are surface-dependent, highlighting the relevance of using human-derived primary cells as a target.

Unraveling the micro- and nanoplastic predicament: A human-centric insight

Micro- and nanoplastics are vast anthropogenic pollutants in our direct surroundings with a robust environmental stability and a potential for a long-lasting and increasing global circulation. This has raised concerns among the public and policy makers for human health upon exposure to these particles. The micro- and nanoplastic burden on humans is currently under debate, along with criticism on the experimental approaches used in hazard assessment. The present review presents an overview of the human-relevant aspects associated with the current micro-and nanoplastic burden. We focus on environmental circulation and the estimation of exposure quantities to humans, along with a state-of-the-art overview of particle accumulation in over 15 human organs and other specimen. Additionally, data regarding particle characteristics used in toxicity testing was extracted from 91 studies and discussed considering their environmental and human relevance.

A Multisystemic Approach Revealed Aminated Polystyrene Nanoparticles-Induced Neurotoxicity

Exposure to plastic nanoparticles has dramatically increased in the last 50 years, and there is evidence that plastic nanoparticles can be absorbed by organisms and cross the blood-brain-barrier (BBB). However, their toxic effects, especially on the nervous system, have not yet been extensively investigated, and most of the knowledge is based on studies using different conditions and systems, thus hard to compare. In this work, physicochemical properties of non-modified polystyrene (PS) and amine-functionalized PS (PS-NH2 ) nanoparticles are initially characterized. Advantage of a multisystemic approach is then taken to compare plastic nanoparticles effects in vitro, through cytotoxic readouts in mammalian cell culture, and in vivo, through behavioral readouts in the nematode Caenorhabditis elegans (C. elegans), a powerful 3R-complying model organism for toxicology studies. In vitro experiments in neuroblastoma cells indicate a specific cytotoxic effect of PS-NH2 particles, including a decreased neuronal differentiation and an increased Amyloid β (Aβ) secretion, a sensitive readout correlating with Alzheimer's disease pathology. In parallel, only in vivo treatments with PS-NH2 particles affect C. elegans development, decrease lifespan, and reveal higher sensitivity of animals expressing human Aβ compared to wild-type animals. In summary, the multisystemic approach discloses a neurotoxic effect induced by aminated polystyrene nanoparticles.

An Emerging Role of Micro- and Nanoplastics in Vascular Diseases

Vascular diseases are the leading causes of death worldwide, and they are attributable to multiple pathologies, such as atherosclerosis, diabetes, and chronic obstructive pulmonary disease. Exposure to various environmental contaminants is associated with the development of various diseases, including vascular diseases. Among environmental contaminants, micro- and nanoplastics have gained attention as global environmental risk factors that threaten human health. Recently, extensive research has been conducted on the effects of micro- and nanoplastics on various human diseases, including vascular diseases. In this review, we highlight the effects of micro- and nanoplastics on vascular diseases.

ROS/mtROS promotes TNTs formation via the PI3K/AKT/mTOR pathway to protect against mitochondrial damages in glial cells induced by engineered nanomaterials

BACKGROUND

As the demand and application of engineered nanomaterials have increased, their potential toxicity to the central nervous system has drawn increasing attention. Tunneling nanotubes (TNTs) are novel cell-cell communication that plays a crucial role in pathology and physiology. However, the relationship between TNTs and nanomaterials neurotoxicity remains unclear. Here, three types of commonly used engineered nanomaterials, namely cobalt nanoparticles (CoNPs), titanium dioxide nanoparticles (TiO2NPs), and multi-walled carbon nanotubes (MWCNTs), were selected to address this limitation.

RESULTS

After the complete characterization of the nanomaterials, the induction of TNTs formation with all of the nanomaterials was observed using high-content screening system and confocal microscopy in both primary astrocytes and U251 cells. It was further revealed that TNT formation protected against nanomaterial-induced neurotoxicity due to cell apoptosis and disrupted ATP production. We then determined the mechanism underlying the protective role of TNTs. Since oxidative stress is a common mechanism in nanotoxicity, we first observed a significant increase in total and mitochondrial reactive oxygen species (namely ROS, mtROS), causing mitochondrial damage. Moreover, pretreatment of U251 cells with either the ROS scavenger N-acetylcysteine or the mtROS scavenger mitoquinone attenuated nanomaterial-induced neurotoxicity and TNTs generation, suggesting a central role of ROS in nanomaterials-induced TNTs formation. Furthermore, a vigorous downstream pathway of ROS, the PI3K/AKT/mTOR pathway, was found to be actively involved in nanomaterials-promoted TNTs development, which was abolished by LY294002, Perifosine and Rapamycin, inhibitors of PI3K, AKT, and mTOR, respectively. Finally, western blot analysis demonstrated that ROS and mtROS scavengers suppressed the PI3K/AKT/mTOR pathway, which abrogated TNTs formation.

CONCLUSION

Despite their biophysical properties, various types of nanomaterials promote TNTs formation and mitochondrial transfer, preventing cell apoptosis and disrupting ATP production induced by nanomaterials. ROS/mtROS and the activation of the downstream PI3K/AKT/mTOR pathway are common mechanisms to regulate TNTs formation and mitochondrial transfer. Our study reveals that engineered nanomaterials share the same molecular mechanism of TNTs formation and intercellular mitochondrial transfer, and the proposed adverse outcome pathway contributes to a better understanding of the intercellular protection mechanism against nanomaterials-induced neurotoxicity.

Transport of polystyrene nanoplastics with different functional groups in goethite-coated saturated porous media: Effects of low molecular weight organic acids and physicochemical properties

The influence of low molecular weight organic acids (LMWOAs) and goethite on the migration of nanoplastics in the soil environment remains poorly understood. To elucidate the mechanism of influence, the study investigated the impact of LMWOAs on the migration ability of functionalized polystyrene nanoplastics (PSNPs-NH2/COOH) in quartz sand (QS) and goethite (α-FeOOH)-coated quartz sand (FOS). We investigated the effect of changes in iron valence induced by LMWOAs on the migration of PSNPs. The results revealed that the migration ability of polystyrene nanoplastics (PSNPs) declined as the ionic strength (IS) increased and the pH decreased, primarily due to the compression of the double layer and protonation reactions. The migration of PSNPs is facilitated by LMWOAs through distinct mechanisms in the two media. Specifically, LMWOAs were adsorbed on the FOS and QS surfaces through complexation and hydrogen bonding, respectively. At pH 4.0, LMWOAs exhibit redox activity, resulting in the generation of additional Fe(III). This redox process enhances the electrostatic attraction between the media and PSNPs, thereby reducing the competition at specific points and spatial resistance associated with LMWOAs. In contrast to FOS, LMWOAs at pH 4.0 reduced the migration ability of PSNPs in QS, following the trend of MA > TA > CA. This difference was attributed to the pKa of LMWOAs and the weak hydrogen bonding on the QS surface. The relevant mathematical models effectively validate the migration results. The above conclusions suggest that LMWOAs can alter the valence state of iron on the surface of goethite, thereby influencing the migration of plastic particles in environmental media.

Embryonic exposure of polystyrene nanoplastics affects cardiac development

Micro- and nanoplastics have recently been detected in human blood and placentas, indicating inevitable embryonic exposure to these particles. However, their influence on human embryogenesis and the underlying mechanisms are still unknown. In this study, the effects of polystyrene nanoplastics (PS-NPs) exposure on cardiac differentiation of human embryonic stem cells (hESCs) were evaluated. Uptake of PS-NPs not only caused cellular injury, but also regulated cardiac-related pathways as revealed by RNA-sequencing. Consequently, the efficiency of cardiomyocyte differentiation from hESCs was compromised, leading to immature of cardiomyocytes and smaller cardiac organoids with impaired contractility. Mechanistically, PS-NPs promoted mitochondrial oxidative stress, activated P38/Erk MAPK signaling pathway, blocked autophagy flux, and eventually reduced the pluripotency of hESCs. Consistently, in vivo exposure of PS-NPs from cleavage to gastrula period of zebrafish embryo led to reduced cardiac contraction and blood flow. Collectively, this study suggests that PS-NPs is a risk factor for fetal health, especially for heart development.

Impact of mucus modulation by N-acetylcysteine on nanoparticle toxicity

Human respiratory mucus is a biological hydrogel that forms a protective barrier for the underlying epithelium. Modulation of the mucus layer has been employed as a strategy to enhance transmucosal drug carrier transport. However, a drawback of this strategy is a potential reduction of the mucus barrier properties, in particular in situations with an increased exposure to particles. In this study, we investigated the impact of mucus modulation on its protective role. In vitro mucus was produced by Calu-3 cells, cultivated at the air-liquid interface for 21 days and used for further testing as formed on top of the cells. Analysis of confocal 3D imaging data revealed that after 21 days Calu-3 cells secrete a mucus layer with a thickness of 24 ± 6 μm. Mucus appeared to restrict penetration of 500 nm carboxyl-modified polystyrene particles to the upper 5-10 μm of the layer. Furthermore, a mucus modulation protocol using aerosolized N-acetylcysteine (NAC) was developed. This treatment enhanced the penetration of particles through the mucus down to deeper layers by means of the mucolytic action of NAC. These findings were supported by cytotoxicity data, indicating that intact mucus protects the underlying epithelium from particle-induced effects on membrane integrity. The impact of NAC treatment on the protective properties of mucus was probed by using 50 and 100 nm amine-modified and 50 nm carboxyl-modified polystyrene nanoparticles, respectively. Cytotoxicity was only induced by the amine-modified particles in combination with NAC treatment, implying a reduced protective function of modulated mucus. Overall, our data emphasize the importance of integrating an assessment of the protective function of mucus into the development of therapy approaches involving mucus modulation.

Micro- and nanoplastics (MNPs) and their potential toxicological outcomes: State of science, knowledge gaps and research needs

Plastic waste has been produced at a rapidly growing rate over the past several decades. The environmental impacts of plastic waste on marine and terrestrial ecosystems have been recognized for years. Recently, researchers found that micro- and nanoplastics (MNPs), micron (100 nm - 5 mm) and nanometer (1 - 100 nm) scale particles and fibers produced by degradation and fragmentation of plastic waste in the environment, have become an important emerging environmental and food chain contaminant with uncertain consequences for human health. This review provides a comprehensive summary of recent findings from studies of potential toxicity and adverse health impacts of MNPs in terrestrial mammals, including studies in both in vitro cellular and in vivo mammalian models. Also reviewed here are recently released biomonitoring studies that have characterized the bioaccumulation, biodistribution, and excretion of MNPs in humans. The majority MNPs in the environment to which humans are most likely to be exposed, are of irregular shapes, varied sizes, and mixed compositions, and are defined as secondary MNPs. However, the MNPs used in most toxicity studies to date were commercially available primary MNPs of polystyrene (PS), polyethylene (PE), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and other polymers. The emerging in vitro and in vivo evidence reviewed here suggests that MNP toxicity and bioactivity are largely determined by MNP particle physico-chemical characteristics, including size, shape, polymer type, and surface properties. For human exposure, MNPs have been identified in human blood, urine, feces, and placenta, which pose potential health risks. The evidence to date suggests that the mechanisms underlying MNP toxicity at the cellular level are primarily driven by oxidative stress. Nonetheless, large knowledge gaps in our understanding of MNP toxicity and the potential health impacts of MNP exposures still exist and much further study is needed to bridge those gaps. This includes human population exposure studies to determine the environmentally relevant MNP polymers and exposure concentrations and durations for toxicity studies, as well as toxicity studies employing environmentally relevant MNPs, with surface chemistries and other physico-chemical properties consistent with MNP particles in the environment. It is especially important to obtain comprehensive toxicological data for these MNPs to understand the range and extent of potential adverse impacts of microplastic pollutants on humans and other organisms.

Uptake and effects of polystyrene nanoplastics in comparison to non-plastic silica nanoparticles on small intestine cells (IPEC-J2)

Nanoplastics smaller than 1 µm accumulate as anthropogenic material in the food chain, but only little is known about their uptake and possible effects on potentially strongly exposed cells of the small intestine. The aim of the study was to observe the uptake of 100 nm polystyrene nanoplastics into a non-tumorigenic small intestine cell culture model (IPEC-J2 cells) and to monitor the effects on cell growth and gene regulation, compared to a 100 nm non-plastic silica nanoparticle reference. The intracellular uptake of both types of nanoparticles was proven via (confocal) fluorescence microscopy and complemented with transmission electron microscopy. Fluorescence microscopy showed a growth phase-dependent uptake of nanoparticles into the cells, hence further experiments included different time points related to epithelial closure, determined via electric cell substrate impedance sensing. No retardations in epithelial closure of cells after treatment with polystyrene nanoparticles could be found. In contrast, epithelial cell closure was partly negatively influenced by silica nanoparticles. An increased production of organic nanoparticles, like extracellular vesicles, was not measurable via nanoparticle tracking analysis. An assessment of messenger RNA by next generation sequencing and subsequent pathway analysis revealed that the TP53 pathway was influenced significantly by the polystyrene nanoparticle treatment. In both treatments, dysregulated mRNAs were highly enriched in the NOTCH signaling pathway compared to the non-particle control.

Hazard Assessment of Polystyrene Nanoplastics in Primary Human Nasal Epithelial Cells, Focusing on the Autophagic Effects

The human health risks posed by micro/nanoplastics (MNPLs), as emerging pollutants of environmental/health concern, need to be urgently addressed as part of a needed hazard assessment. The routes of MNPL exposure in humans could mainly come from oral, inhalation, or dermal means. Among them, inhalation exposure to MNPLs is the least studied area, even though their widespread presence in the air is dramatically increasing. In this context, this study focused on the potential hazard of polystyrene nanoplastics (PSNPLs with sizes 50 and 500 nm) in human primary nasal epithelial cells (HNEpCs), with the first line of cells acting as a physical and immune barrier in the respiratory system. Primarily, cellular internalization was evaluated by utilizing laboratory-labeled fluorescence PSNPLs with iDye, a commercial, pink-colored dye, using confocal microscopy, and found PSNPLs to be significantly internalized by HNEpCs. After, various cellular effects, such as the induction of intracellular reactive oxygen species (iROS), the loss of mitochondrial membrane potential (MMP), and the modulation of the autophagy pathway in the form of the accumulation of autophagosomes (LC3-II) and p62 markers (a ubiquitin involved in the clearance of cell debris), were evaluated after cell exposure. The data demonstrated significant increases in iROS, a decrease in MMP, as well as a greater accumulation of LC3-II and p62 in the presence of PSNPLs. Notably, the autophagic effects did indicate the implications of PSNPLs in defective or insufficient autophagy. This is the first study showing the autophagy pathway as a possible target for PSNPL-induced adverse effects in HNEpCs. When taken together, this study proved the cellular effects of PSNPLs in HNEpCs and adds value to the existing studies as a part of the respiratory risk assessment of MNPLs.