Cationic nanoplastic causes mitochondrial dysfunction in neural progenitor cells and impairs hippocampal neurogenesis

Exposure to polystyrene nanoplastics promotes premature cellular senescence through mitochondrial ROS production and dysfunction in pre-differentiated skeletal myoblasts

Nanoplastics (NPs) are emerging environmental contaminants present in atmospheric, freshwater, and aquatic environments. NPs can rapidly permeate cell membranes and build up in human tissues and organs, causing a potential threat to human health. As the skeletal muscle undergoes aging, myogenesis gradually deteriorates, leading to loss of muscle mass. While previous studies have demonstrated the adverse and toxic effects of polystyrene (PS)-NPs, gaps remain in understanding aging effects and specific mechanisms by PS-NPs in pre-differentiated myoblasts. In this study, we investigated the cellular internalization, aggregation, and senescent effects of PS-NPs using an in vitro model of pre-differentiated C2C12 myoblasts. Pre-differentiated C2C12 myoblasts were exposed to increasing concentrations of PS-NPs and internalization was observed in myoblasts using flow cytometry and transmission electron microscopy (TEM). We further investigated whether internalization of these PS-NPs at sublethal cytotoxic concentrations led to an increase in senescence hallmarks, such as increased β-galactosidase activity, increased expression of p16, p21 and senescence-related secretory phenotypes, and cell cycle arrest. In addition, PS-NP treatment caused notable mitochondrial superoxide production and damage, including mitochondrial membrane depolarization, content loss, fragmentation, and decreased ATP production. Rotenone, a mitochondrial function inhibitor, and exacerbated PS-NP-induced cell proliferation inhibition, whereas Mito-TEMPO, a mitochondrial superoxide scavenger, restored the cell proliferation rate and rescued cellular senescence. Therefore, our findings indicate the senescent effects of PS-NPs through mitochondrial superoxide production and dysfunction in pre-differentiated myoblasts.

Assessment of the neurotoxicity of monosodium glutamate on neural stem cells and hippocampal neurogenesis in a rodent model

Monosodium glutamate (MSG) is a widely used flavor enhancer in processed foods and valued for its ability to enhance the savory taste known as umami. MSG is classified as non-toxic and recognized as a safe food additive with no specific usage restrictions in many countries. However, neurotoxic studies on MSG have primarily focused on neurons, and the effects of MSG on neural stem cells (NSCs) have not been reported. This study aimed to evaluate the neurotoxic effect of MSG on NSCs and hippocampal neurogenesis in a rodent model. In vitro studies showed that MSG induces cytotoxicity in primary neuron cultures but has no toxic effect on NSCs. Furthermore, in vivo studies on 4-week-old male C57BL/6 mice orally administered MSG and sodium chloride (NaCl) for two weeks revealed that neither MSG nor NaCl induced changes in the expressions of neuronal markers or glutamate receptors in the hippocampus. In addition, no differences in NSC proliferation or survival were detected, and MSG did not adversely affect the neuronal differentiation of NSCs. Moreover, neurobehavioral tests showed that MSG treatment did not impair spatial learning and memory. These findings provide a first assessment of the neurotoxic effects of MSG on NSCs and hippocampal neurogenesis.

Microplastics/nanoplastics and neurological health: An overview of neurological defects and mechanisms

The widespread use of plastic products worldwide has brought about serious environmental issues. In natural environments, it's difficult for plastic products to degrade completely, and so they exist in the form of micro/nanoplastics (M/NPs), which have become a new type of pollutant. Prolonged exposure to M/NPs can lead to a series of health problems in humans, particularly toxicity to the nervous system, with consequences including neurodevelopmental abnormalities, neuronal death, neurological inflammation, and neurodegenerative diseases. Although direct evidence from humans is still limited, model organisms and organoids serve as powerful tools to provide important insights. This article summarizes the effects of M/NPs on the nervous system, focusing on cognitive function, neural development, and neuronal death. Mechanisms such as neurotransmitter synthesis and release, inflammatory responses, oxidative stress, the gut-brain axis, and the liver-brain axis are covered. The neurotoxicity induced by M/NPs may exacerbate or directly trigger neurodegenerative diseases and neurodevelopmental disorders. We particularly emphasize potential therapeutic agents that may counteract the neurotoxic effects induced by M/NPs, highlighting a novel future research direction. In summary, this paper cites evidence and provides mechanistic perspectives on the effects of M/NPs on neurological health, providing clues for eliminating M/NP hazards to human health in the future.

PMMA nanoplastics induce gastric epithelial cellular senescence and cGAS-STING-mediated inflammation via ROS overproduction and NHEJ suppression

The increasing environmental presence of nanoplastics (NPs) has raised concerns about their potential impact on biological systems. We investigated the repercussions of polymethyl methacrylate (PMMA) NPs exposure on normal gastric epithelial cells and revealed a pronounced increase in senescence-associated β-galactosidase activity and G1 phase cell cycle arrest. Our study demonstrated a dose-dependent increase in reactive oxygen species (ROS) and DNA damage, underscoring the pivotal role of ROS in PMMA NPs-mediated effects, a novel contribution to the existing body of knowledge dominated by polystyrene particles. Furthermore, we explored the influence of PMMA NPs on DNA damage response mechanisms, highlighting the significant inhibition of nonhomologous end-joining (NHEJ). Our findings help to elucidate the consequent genomic instability, as evidenced by increased chromosomal aberrations and micronuclei formation. By connecting these cellular manifestations to organism-level effects, we hypothesize that PMMA NPs play a critical role in aging processes. Our work revealed an activated cGAS-STING signaling pathway after PMMA NPs exposure, which correlated with aging-related inflammation and behavioral changes in mice. Importantly, our study provides comprehensive evidence of PMMA NPs-induced premature aging in gastric epithelial cells, shedding light on the molecular intricacies underlying DNA damage, repair impairment, and inflammation. Our research prompts heightened caution regarding the risks of NPs exposure and calls for further investigation into the broader implications of these environmental pollutants on aging processes in higher organisms.

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.

Cytotoxicity of amine-modified polystyrene MPs and NPs on neural stem cells cultured from mouse subventricular zone

Microplastics (MPs) and nanoplastics (NPs) are found in various environments such as aquatic, terrestrial, and aerial areas. Once ingested and inhaled, these tiny plastic debris damaged the digestive and respiratory organ systems in animals. In humans, the possible connection between MPs and various diseases such as lung diseases has been raised. Yet, the impact of MPs on the human nervous system has been unclear. Previous research using animals and cultured cells showed possible neurotoxicity of MPs and NPs. In this study, we used neural stem cells cultured from mouse subventricular zone to examine the effects of polystyrene (PS) NPs and MPs with sizes of 0.1 μm, 1 μm, and 2 μm on the cell proliferation and differentiation. We observed that only positively charged NPs and MPs, but not negatively charged ones, decreased cell viability and proliferation. These amine-modified NPs and MPs decreased both neurogenesis and oligodendrogenesis. Finally, fully differentiated neurons and oligodendrocytes were damaged and removed by the application of NPs and MPs. All these effects varied among different sizes of NPs and MPs, with the greatest effects from 1 μm and the least effects from 2 μm. These results clearly demonstrate the cytotoxicity and neurotoxicity of PS-NPs and MPs.

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.