Toxicity and Biodistribution of Fragmented Polypropylene Microplastics in ICR Mice

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.

Oral subacute polypropylene microplastics administration effect on potential immunotoxicity in ICR mice

Exposure to microplastics may be associated with damage of immune system. Polypropylene microplastics (PP-MPs) with a wide range of beneficial applications have not been extensively studied with respect to the immune system. The aim of this investigation is to examine the influence of two different sizes of PP-MPs (5.2 and 23.9 μm diameter) on immune system components in ICR mice. PP-MPs were administered orally to female and male mice at 0 (corn oil vehicle), 500, 1000, or 2000 mg/kg/d for single and daily for 4-week repeated toxicity test, respectively. No significant differences were observed in number of thymic CD4+, CD8+, CD4+CD8+ T lymphocytes, splenic helper T cells, cytotoxic T cells, and B cells. The ratio of interferon-γ to interleukin-4 in culture supernatants from activated splenocytes ex vivo (48 hr) was lower in females which were repeatedly administered with PP-MPs compared to vehicle irrespective of PP-MPs size and dose. In contrast, the opposite trend was observed in males. Production of tumor necrosis factor-α was upregulated in females that were repeatedly exposed to PP-MPs. The serum IgG2a/IgG1 ratio was lowered in female receiving large-size PP-MPs. Data suggest that immune disturbances resulting in predominant type-2 helper T cell reactivity may occur in mice, especially in females, when repeatedly exposed to PP-MPs. Further investigations with longer exposure periods are necessary to determine the immunotoxicities attributed to PP-MPs.

Exploring the potential and challenges of developing physiologically-based toxicokinetic models to support human health risk assessment of microplastic and nanoplastic particles

Microplastics (MPs) and nanoplastics (NPs) pollution has emerged as a significant and widespread environmental issue. Humans are inevitably exposed to MPs and NPs via ingestion, inhalation, and dermal contacts from various sources. However, mechanistic knowledge of their distribution, interaction, and potency in the body is still lacking. To address this knowledge gap, we have undertaken the task of elucidating the toxicokinetic (TK) behaviors of MPs and NPs, aiming to provide mechanistic information for constructing a conceptual physiologically based toxicokinetic (PBTK) model to support in silico modeling approaches. Our effort involved a thorough examination of the existing literature and data collation on the presence of MPs in the human body and in vitro/ex vivo/in vivo biodistribution across various cells and tissues. By comprehending the absorption, distribution, metabolism, and excretion mechanisms of MPs and NPs in relation to their physicochemical attributes, we established a foundational understanding of the link between external exposure and internal tissue dosimetry. We observed that particle size and surface chemistry have been thoroughly explored in previous experimental studies. However, certain attributes, such as polymer type, shape, and biofilm/biocorona, warrant attention and further examination. We discussed the fundamental disparities in TK properties of MPs/NPs from those of engineered nanoparticles. We proposed a preliminary PBTK framework with several possible modeling approaches and discussed existing challenges for further investigation. Overall, this article provides a comprehensive compilation of existing TK data of MPs/NPs, a critical overview of TK processes and mechanisms, and proposes potential PBTK modeling approaches, particularly regarding their applicability to the human system, and outlines future perspectives for developing PBTK models and their integration into human health risk assessment of MPs and NPs.

Pulmonary toxicity assessment of polypropylene, polystyrene, and polyethylene microplastic fragments in mice

Polypropylene (PP), polystyrene (PS), and polyethylene (PE) plastics are commonly used in household items such as electronic housings, food packaging, bottles, bags, toys, and roofing membranes. The presence of inhalable microplastics in indoor air has become a topic of concern as many people spent extended periods of time indoors during the COVID-19 pandemic lockdown restrictions, however, the toxic effects on the respiratory system are not properly understood. We examined the toxicity of PP, PS, and PE microplastic fragments in the pulmonary system of C57BL/6 mice. For 14 days, mice were intratracheally instilled 5 mg/kg PP, PS, and PE daily. The number of inflammatory cells such as macrophages, neutrophils, and eosinophils in the bronchoalveolar lavage fluid (BALF) of PS-instilled mice was significantly higher than that in the vehicle control (VC). The levels of inflammatory cytokines and chemokines in BALF of PS-instilled mice increased compared to the VC. However, the inflammatory responses in PP- and PE-stimulated mice were not significantly different from those in the VC group. We observed elevated protein levels of toll-like receptor (TLR) 2 in the lung tissue of PP-instilled mice and TLR4 in the lung tissue of PS-instilled mice compared with those to the VC, while TLR1, TLR5, and TLR6 protein levels remained unchanged. Phosphorylation of nuclear factor kappa B (NF-κB) and IĸB-α increased significantly in PS-instilled mice compared with that in VC. Furthermore, Nucleotide‑binding oligomerization domain‑like receptor family pyrin domain‑containing 3 (NLRP3) inflammasome components including NLRP3, apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), and Caspase-1 in the lung tissue of PS-instilled mice increased compared with that in the VC, but not in PP- and PE-instilled mice. These results suggest that PS microplastic fragment stimulation induces pulmonary inflammation due to NF-ĸB and NLRP3 inflammasome activation by the TLR4 pathway.

Supplementary Information

The online version contains supplementary material available at 10.1007/s43188-023-00224-x.

The release of polypropylene plastic from disposable face masks in different water conditions and their potential toxicity in human cells

Due to their extensive use during and after the COVID-19 pandemic, many disposable face masks are irresponsibly deposited into the water environment, threatening the health of people living nearby. However, the effects of water conditions on the degradation and potential hazards of these masks are generally unclear. This paper entailed the release and cellular toxicity of micro/nano plastics from disposable face masks once discarded in different waters, including soil water, river water, and tap water, with deionized (DI) water as control. At first, polypropylene (PP) was confirmed to be the major component of disposable face masks with Raman and Fourier transform infrared (FTIR) techniques. To monitor the release rate of PP from masks, a silver nanoparticle (AgNP)-based surface-enhanced Raman scattering (SERS) method was established by employing the unique Raman fingerprint of PP at 2882 cm-1. During 30-d incubation in different waters, the release rates of PP, sizes of PP aggregates, length of fibers, and proportions of plastics smaller than 100 nm were in the order of soil water > river water > tap water > DI water. All the obtained PP exhibited significant toxicity in human lung cancer (A549) cells at concentrations of 70 mg/L for 48 h, and the ones obtained in soil water exhibited the most severe damage. Overall, this paper revealed that environmental waters themselves would worsen the adverse effects of disposable face masks, and the key compounds affecting the degradation of masks remain to be clarified. Such information, along with the established methods, could be beneficial in assessing the health risks of disposable face masks in different waters.

Adverse Effects of Micro- and Nanoplastics on Humans and the Environment

The pervasive pollution caused by nano- and microplastics (N/MPLs) is a pressing concern, and was exacerbated during the COVID-19 pandemic due to the substantial release of disposable Personal Protective Equipment (PPE) into the environment [...].