Investigation of nanoplastic cytotoxicity using SH-SY5Y human neuroblastoma cells and polystyrene nanoparticles

ROS-dependent degeneration of human neurons induced by environmentally relevant levels of micro- and nanoplastics of diverse shapes and forms

Our study explores the pressing issue of micro- and nanoplastics (MNPs) inhalation and their subsequent penetration into the brain, highlighting a significant environmental health concern. We demonstrate that MNPs can indeed penetrate murine brain, warranting further investigation into their neurotoxic effects in humans. We then proceed to test the impact of MNPs at environmentally relevant concentrations, with focusing on variations in size and shape. Our findings reveal that these MNPs induce oxidative stress, cytotoxicity, and neurodegeneration in human neurons, with cortical neurons being more susceptible than nociceptors. Furthermore, we examine the role of biofilms on MNPs, demonstrating that MNPs can serve as a vehicle for pathogenic biofilms that significantly exacerbate these neurotoxic effects. This sequence of investigations reveals that minimal MNPs accumulation can cause oxidative stress and neurodegeneration in human neurons, significantly risking brain health and highlights the need to understand the neurological consequences of inhaling MNPs. Overall, our developed in vitro testing battery has significance in elucidating the effects of environmental factors and their associated pathological mechanisms in human neurons.

Neurotoxicities induced by micro/nanoplastics: A review focusing on the risks of neurological diseases

Pollution of micro/nano-plastics (MPs/NPs) is ubiquitously prevalent in the environment, leading to an unavoidable exposure of the human body. Despite the protection of the blood-brain barrier, MPs/NPs can be transferred and accumulated in the brain, which subsequently exert negative effects on the brain. Nevertheless, the potential neurodevelopmental and/or neurodegenerative risks of MPs/NPs remain largely unexplored. In this review, we provide a systematic overview of recent studies related to the neurotoxicity of MPs/NPs. It covers the environmental hazards and human exposure pathways, translocation and distribution into the brain, the neurotoxic effects, and the possible mechanisms of environmental MPs/NPs. MPs/NPs are widely found in different environment matrices, including air, water, soil, and human food. Ambient MPs/NPs can enter the human body by ingestion, inhalation and dermal contact, then be transferred into the brain via the blood circulation and nerve pathways. When MPs/NPs are present in the brain, they can initiate a series of molecular or cellular reactions that may harm the blood-brain barrier, cause oxidative stress, trigger inflammatory responses, affect acetylcholinesterase activity, lead to mitochondrial dysfunction, and impair autophagy. This can result in abnormal protein folding, loss of neurons, disruptions in neurotransmitters, and unusual behaviours, ultimately contributing to the initiation and progression of neurodegenerative changes and neurodevelopmental abnormalities. Key challenges and further research directions are also proposed in this review as more studies are needed to focus on the potential neurotoxicity of MPs/NPs under realistic conditions.

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

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

Genotoxic and neurotoxic potential of intracellular nanoplastics: A review

Plastic waste comprises polymers of different chemicals that disintegrate into nanoplastic particles (NPLs) of 1-100-nm size, thereby littering the environment and posing a threat to wildlife and human health. Research on NPL contamination has up to now focused on the ecotoxicology effects of the pollution rather than the health risks. This review aimed to speculate about the possible properties of carcinogenic and neurotoxic NPL as pollutants. Given their low-dimensional size and high surface size ratio, NPLs can easily penetrate biological membranes to cause functional and structural damage in cells. Once inside the cell, NPLs can interrupt the autophagy flux of cellular debris, alter proteostasis, provoke mitochondrial dysfunctions, and induce endoplasmic reticulum stress. Harmful metabolic and biological processes induced by NPLs include oxidative stress (OS), ROS generation, and pro-inflammatory reactions. Depending on the cell cycle status, NPLs may direct DNA damage, tumorigenesis, and lately carcinogenesis in tissues with high self-renewal capabilities like epithelia. In cells able to live the longest like neurons, NPLs could trigger neurodegeneration by promoting toxic proteinaceous aggregates, OS, and chronic inflammation. NPL genotoxicity and neurotoxicity are discussed based on the gathered evidence, when available, within the context of the intracellular uptake of these newcomer nanoparticles. In summary, this review explains how the risk evaluation of NPL pollution for human health may benefit from accurately monitoring NPL toxicokinetics and toxicodynamics at the intracellular resolution level.

The weakened physiological functions of human serum albumin in presence of polystyrene nanoplastics

Due to the widespread presence of nanoplastics (NPs) in daily essentials and drinking water, the potential adverse effects of NPs on human health have become a global concern. Human serum albumin (HSA), the most abundant and multi-functional protein in plasma, has been chosen to understand the biological effects of NPs after entering the blood. The esterase activity and the transport of bisphenol A in the presence of polystyrene nanoplastics (PSNPs) under physiological conditions (pH 4.0 and 7.4) have been investigated to evaluate the possible biological effects. The interactions between PSNPs and HSA have also been systematically studied by multispectral methods and dynamic light scattering techniques. The esterase activity of HSA presented a decreased trend with increasing PSNPs; conversely, higher permeabilities are accompanied by higher amounts of PSNPs. Compared with the unchanged hydrodynamic diameter and weaker interactions at pH 7.4, stronger binding between HSA and PSNPs at pH 4.0 led to a significant increase in the particle size of the PSNPs-HSA complex. The quenching mechanism belonged to the static quenching type. The electrostatic force is proposed to be the dominant factor for PSNPs binding to HSA. The work provides some information about the toxicity of NPs when exposed to humans.

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.

Effect of Acrylamide and Mycotoxins in SH-SY5Y Cells: A Review

Thermal processes induce the formation of undesired toxic components, such as acrylamide (AA), which has been shown to induce brain toxicity in humans and classified as Group 2A by the International Agency of Research in Cancer (IARC), as well as some mycotoxins. AA and mycotoxins' toxicity is studied in several in vitro models, including the neuroblastoma cell line model SH-SY5Y cells. Both AA and mycotoxins occur together in the same food matrix cereal base (bread, pasta, potatoes, coffee roasting, etc.). Therefore, the goal of this review is to deepen the knowledge about the neurological effects that AA and mycotoxins can induce on the in vitro model SH-SY5Y and its mechanism of action (MoA) focusing on the experimental assays reported in publications of the last 10 years. The analysis of the latest publications shows that most of them are focused on cytotoxicity, apoptosis, and alteration in protein expression, while others are interested in oxidative stress, axonopathy, and the disruption of neurite outgrowth. While both AA and mycotoxins have been studied in SH-SY5Y cells separately, the mixture of them is starting to draw the interest of the scientific community. This highlights a new and interesting field to explore due to the findings reported in several publications that can be compared and the implications in human health that both could cause. In relation to the assays used, the most employed were the MTT, axonopathy, and qPCR assays. The concentration dose range studied was 0.1-10 mM for AA and 2 fM to 200 µM depending on the toxicity and time of exposure for mycotoxins. A healthy and varied diet allows the incorporation of a large family of bioactive compounds that can mitigate the toxic effects associated with contaminants present in food. Although this has been reported in some publications for mycotoxins, there is still a big gap for AA which evidences that more investigations are needed to better explore the risks for human health when exposed to AA and mycotoxins.

Polystyrene nanoparticles induced mammalian intestine damage caused by blockage of BNIP3/NIX-mediated mitophagy and gut microbiota alteration

Nanoplastics possess the capacity for cellular internalization, and consequentially disrupt mitochondrial functionality, precipitating aberrations in energy metabolism. Given this, the potential accumulation of nanoplastics in alimentary sources presents a considerable hazard to the mammalian gastrointestinal system. While mitophagy serves as a cytoprotective mechanism that sustains redox homeostasis through the targeted removal of compromised mitochondria, the regulatory implications of mitophagy in nanoplastic-induced toxicity remain an underexplored domain. In the present investigation, polystyrene (PS) nanoparticles, with a diameter of 80 nm employed as a representative model to assess their toxicological impact and propensity to instigate mitophagy in intestinal cells both in vitro and in vivo. Data indicated that PS nanoparticles elicited BNIP3/NIX-mediated mitophagy within the intestinal milieu. Strikingly, the impediment of this degradation process at elevated concentrations was correlated with exacerbated pathological ramifications. In vitro assays corroborated that high-dosage cellular uptake of PS nanoparticles obstructed the mitophagy pathway. Furthermore, treatment with PS nanoparticles engendered alterations in gut microbiota composition and manifested a proclivity to modulate nutritional metabolism. Collectively, these findings elucidate that oral exposure to PS nanoparticles culminates in the inhibition of mitophagy and induces perturbations in the intestinal microbiota. This contributes valuable insights into the toxicological repercussions of nanoplastics on mammalian gastrointestinal health.

PLASTAMINATION: Outcomes on the Central Nervous System and Reproduction

BACKGROUND

Environmental exposures to non-biodegradable and biodegradable plastics are unavoidable. Microplastics (MPs) and nanoplastics (NPs) from the manufacturing of plastics (primary sources) and the degradation of plastic waste (secondary sources) can enter the food chain directly or indirectly and, passing biological barriers, could target both the brain and the gonads. Hence, the worldwide diffusion of environmental plastic contamination (PLASTAMINATION) in daily life may represent a possible and potentially serious risk to human health.

OBJECTIVE

This review provides an overview of the effects of non-biodegradable and the more recently introduced biodegradable MPs and NPs on the brain and brain-dependent reproductive functions, summarizing the molecular mechanisms and outcomes on nervous and reproductive organs. Data from in vitro, ex vivo, non-mammalian and mammalian animal models and epidemiological studies have been reviewed and discussed.

RESULTS

MPs and NPs from non-biodegradable plastics affect organs, tissues and cells from sensitive systems such as the brain and reproductive organs. Both MPs and NPs induce oxidative stress, chronic inflammation, energy metabolism disorders, mitochondrial dysfunction and cytotoxicity, which in turn are responsible for neuroinflammation, dysregulation of synaptic functions, metabolic dysbiosis, poor gamete quality, and neuronal and reproductive toxicity. In spite of this mechanistic knowledge gained from studies of non-biodegradable plastics, relatively little is known about the adverse effects or molecular mechanisms of MPs and NPs from biodegradable plastics.

CONCLUSION

The neurological and reproductive health risks of MPs/NPs exposure warrant serious consideration, and further studies on biodegradable plastics are recommended.

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.

In vitro wheat protoplast cytotoxicity of polystyrene nanoplastics

Nanoplastics are an emerging environmental pollutant, having a potential risk to the terrestrial ecosystem. In the natural environment, almost all the micro-or nano-plastics will be aged by many factors and their characterizations of the surface will be modified. However, the toxicity and mechanism of the modified polystyrene nanoparticles (PS-NPs) to plant cells are not clear. In the study, the amino- and carboxyl-modified PS-NPs with different sizes (20 and 200 nm) were selected as the typical representatives to investigate their effects on protoplast cell viability, reactive oxygen species (ROS) production in the cell and the leakage of cell-inclusion and apoptosis. The results indicated that the 20 nm amino-modified PS-NPs (PS-20A) could significantly damage the structure of the cell, especially the cell membrane, chloroplast and mitochondrion. After being modified by amino group, smaller size nanoplastics had the potential to cause more severe damage. In addition, compared with carboxyl-modified PS-NPs, the amino-modified PS-NPs induced more ROS production and caused higher membrane permeability/lactate dehydrogenase (LDH) leakage. Apoptosis assay indicated that the proportion of viable cells in the PS-20A treatment decreased significantly, and the proportion of necrotic cells increased by four times. This study provides new insights into the toxicity and damage mechanism of PS-NPs to terrestrial vascular plants at the cellular level, and guides people to pay attention to the quality and safety of agricultural products caused by nanoplastics.

A review of potential human health impacts of micro- and nanoplastics exposure

This systematic review aims to summarize the current knowledge on biological effects of micro- and nanoplastics (MNPs) on human health based on mammalian systems. An extensive search of the literature led to a total of 133 primary research articles on the health relevance of MNPs. Our findings revealed that although the study of MNP cytotoxicity and inflammatory response represents a major research theme, most studies (105 articles) focused on the effects of polystyrene MNPs due to their wide availability as a well characterised research material that can be manufactured with a large range of particle sizes, fluorescence labelling as well as various surface modifications. Among the 133 studies covered in this review, 117 articles reported adverse health effects after being exposed to MNPs. Mammalian in vitro studies identified multiple biological effects including cytotoxicity, oxidative stress, inflammatory response, genotoxicity, embryotoxicity, hepatotoxicity, neurotoxicity, renal toxicity and even carcinogenicity, while rodent in vivo models confirmed the bioaccumulation of MNPs in the liver, spleen, kidney, brain, lung and gut, presenting adverse effects at different levels including reproductive toxic effects and trans-generational toxicity. In contrast, the remaining 16 studies indicated an insignificant impact of MNPs on humans. A few studies attempted to investigate the mechanisms or factors driving the toxicity of MNPs and identified several determining factors including size, concentration, shape, surface charge, attached pollutants and weathering process, which, however, were not benchmarked or considered by most studies. This review demonstrates that there are still many inconsistencies in the evaluation of the potential health effects of MNPs due to the lack of comparability between studies. Current limitations hindering the attainment of reproducible conclusions as well as recommendations for future research directions are also presented.

A review on the impacts of nanomaterials on neuromodulation and neurological dysfunction using a zebrafish animal model

Nanomaterials have been widely employed from industrial to medical fields due to their small sizes and versatile characteristics. However, nanomaterials can also induce unexpected adverse effects on health. In particular, exposure of the nervous system to nanomaterials can cause serious neurological dysfunctions and neurodegenerative diseases. A number of studies have adopted various animal models to evaluate the neurotoxic effects of nanomaterials. Among them, zebrafish has become an attractive animal model for neurotoxicological studies due to several advantages, including the well-characterized nervous system, efficient genome editing, convenient generation of transgenic lines, high-resolution in vivo imaging, and an array of behavioral assays. In this review, we summarize recent studies on the neurotoxicological effects of nanomaterials, particularly engineered nanomaterials and nanoplastics, using zebrafish and discuss key findings with advantages and limitations of the zebrafish model in neurotoxicological studies.

Bioanalytical approaches for the detection, characterization, and risk assessment of micro/nanoplastics in agriculture and food systems

This review discusses the most recent literature (mostly since 2019) on the presence and impact of microplastics (MPs, particle size of 1 μm to 5 mm) and nanoplastics (NPs, particle size of 1 to 1000 nm) throughout the agricultural and food supply chain, focusing on the methods and technologies for the detection and characterization of these materials at key entry points. Methods for the detection of M/NPs include electron and atomic force microscopy, vibrational spectroscopy (FTIR and Raman), hyperspectral (bright field and dark field) and fluorescence imaging, and pyrolysis-gas chromatography coupled to mass spectrometry. Microfluidic biosensors and risk assessment assays of MP/NP for in vitro, in vivo, and in silico models have also been used. Advantages and limitations of each method or approach in specific application scenarios are discussed to highlight the scientific and technological obstacles to be overcome in future research. Although progress in recent years has increased our understanding of the mechanisms and the extent to which MP/NP affects health and the environment, many challenges remain largely due to the lack of standardized and reliable detection and characterization methods. Most of the methods available today are low-throughput, which limits their practical application to food and agricultural samples. Development of rapid and high-throughput field-deployable methods for onsite screening of MP/NPs is therefore a high priority. Based on the current literature, we conclude that detecting the presence and understanding the impact of MP/NP throughout the agricultural and food supply chain require the development of novel deployable analytical methods and sensors, the combination of high-precision lab analysis with rapid onsite screening, and a data hub(s) that hosts and curates data for future analysis.