Nano polystyrene induced changes in anxiety and learning behaviour are mediated through oxidative stress and gene disturbance in mouse brain regions

Microplastic pollution: a review of specific blood-tissue barrier breaches and health effects

Microplastic (1 μm - 5 mm) and nanoplastic (<1 μm) pollution is a heightening global challenge affecting the environment and the health of living creatures within. As primary precursors for plastic manufacturing, microplastics predominantly get into the environment through plastic product degradation and integrate into water, food chain and consumer products leading to potential health consequences. The mammalian system is equipped with several blood-tissue barriers with exclusive tight junctions that selectively regulate material transfer and protect vulnerable and functionally important organs. Nonetheless, emerging evidence indicates microplastics interact, traverse and compromise the integrity of these complex barriers. This review summarises the known and potential impact of microplastics on human health, focusing on specific organ barrier breaches. Evidence of microplastic traversal and deposition in distal mammalian organs are discussed. We further highlight current challenges facing both researchers and clinicians and provide an outlook for expanding our understanding of the impact of microplastic on health.

Lifelong exposure to polystyrene-nanoplastics induces an attention-deficit hyperactivity disorder-like phenotype and impairs brain aging in mice

The accumulation of plastic waste in the environment, breaking down into micro- and nanoplastics, poses significant threats to ecosystem and human health. Plastic particles have been detected in human blood, urine, and placental tissue, indicating widespread exposure. While their long-term health impacts remain unclear, developing brains, especially in fetuses and children, may be vulnerable, potentially resulting in behavioral changes or neurodevelopmental disorders. This study explores the effects of chronic exposure to 23-nm polystyrene nanoplastics at 10 µg/day/kg in wild-type mice across life stages, using exposure levels reflective of human reality. Maternal exposure disrupted critical developmental milestones in pups. In adulthood, exposed mice exhibited Attention-Deficit Hyperactivity Disorder (ADHD)-like traits, including hyperactivity, increased risk-taking behaviors, and impaired motor learning and executive functions. In aging mice, exposure was associated with a lower epileptic threshold, with developing seizures. These behavioral changes were linked to altered gene and synaptic protein expression associated with ADHD and epilepsy. At the cellular level, lifelong nanoplastic exposure caused lysosomal dysfunctions and increased lipofuscin accumulation, indicative of accelerated brain aging. These findings align with the growing prevalence of ADHD and epilepsy in humans, particularly children and the elderly, emphasizing the urgent need to address plastic pollution and its health implications.

Neurobehavioral and neurochemical effects of nano-sized polypropylene accumulation in zebrafish (Danio rerio)

Plastic pollution, particularly nanoplastics (NPs), is a significant environmental contaminant that poses potential toxicological risks to organisms and ecosystems. Although extensive research has been conducted on the toxicity of NPs, our understanding remains limited, primarily because of the constraints of standardized toxicity studies using polymers of specific sizes and types. To address this gap, we conducted toxicity experiments using directly synthesized polypropylene nanoparticles (PP-NPs) in zebrafish (Danio rerio). The presence of PP-NPs in the zebrafish brain was confirmed using pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) and bio-transmission electron microscopy (bio-TEM). The accumulation of PP-NPs in the brain of D. rerio led to neurotoxicity, manifested as reduced motility and aggressiveness. Altered neurotransmitter levels and neural activity associated with behavior further supported these findings. This study suggests that environmental plastic pollutants may accumulate in the brain and cause neurotoxicity in organisms, emphasizing the need for appropriate management of these substances.

Co-exposure to ozone and polystyrene nanoplastic exacerbates cognitive impairment and anxiety-like behavior by regulating neuronal pyroptosis in mice

Ozone (O3) and nanoplastics (NPs) are pervasive environmental pollutants that frequently co-occur in our heavily industrialized era. While it has been documented that exposure to O3 or NPs individually has neurotoxic effects, studies investigating their combined impact and the hazardous mechanisms resulting from co-exposure are limited. In this study, we established a mouse model co-exposure to polystyrene nanoparticles (PS-NPs) and O3, focusing on the prefrontal cortex (PFC), a brain region crucial for cognition and emotion. We examined the effects of O3 and PS-NPs on behavioral changes related to learning, memory, and anxiety, employing transcriptome sequencing alongside molecular and histopathological methods. Our findings indicate that combined exposure to O3 and PS-NPs disrupts the integrity of the blood-brain barrier, reducing Claudin 5 expression and leading to increased accumulation of PS-NPs in the PFC. Transcriptome sequencing demonstrated the involvement of the p38 mitogen-activated protein kinase (p38 MAPK) signaling pathway and oxidative stress in the pathological changes observed in the PFC. Through immunohistochemical and immunofluorescence analysis, we observed enhanced microglial activation, which correlates with increased production of inflammatory factors. Additionally, western blot and immunofluorescence co-labeling analyses revealed elevated expression levels of GSDMD-N, caspase-1, IL-1β, and IL-18 proteins, which are associated with neuronal pyroptosis. Finally, immunofluorescence co-labeling confirmed that the activation of the p38 MAPK pathway in neurons is involved in co-exposure-induced pyroptosis. Meanwhile, N-Acetylcysteine (NAC), a common antioxidant, can alleviate neuroinflammation and neuronal pyroptosis in the PFC, and it rescued the cognitive deficits and anxiety-like behaviors observed in the co-exposed mice. Our study illustrates that co-exposure to O3 and NPs can aggravate damage to the blood-brain barrier and elevate oxidative stress levels in the PFC, thereby increasing the occurrence of neuroinflammation and may mediate neuronal pyroptosis through activation of the p38 MAPK pathway, ultimately contributing to neurobehavioral toxicity.

Prenatal exposure on nanoplastics: A study of spatial transcriptomics in hippocampal offspring

Nanoplastics, as environmental contaminants, are thought to have irreversible impacts on the developing brains of infants and early children; however, the degree of the effects and the mechanisms of damage are unknown. In this study, spatial transcriptomics was used to investigate changes in the hippocampal region of rats descended from maternal exposure to polystyrene nanoplastics (PS-NPs), and the transcriptomes of each spot were sequenced, allowing us to visualize the hippocampus's transcriptional landscape as well as clarify the gene expression profiles of each cell type. Spatial transcriptomics was used to explore changes in the hippocampus region of rats exposed to PS-NPs during brain formation and maturation.The study's findings showed that the offspring hippocampal region had fewer neurons, more astrocytes, and more excitatory neurons 1(ExN1). The pseudo-time study of astrocytes revealed a decrease in C3-type astrocytes and an increase in C2-type astrocytes. This finding raises the possibility that memory impairment in the offspring may result from the developmental obstruction of astrocytes following the intervention of PS-NPs. Moreover, the annotations of four hippocampus regions, CA1, CA2-3, DG, and HILUS, as well as the GO and GSVA of several cell types, revealed deficiencies that can contribute to learning memory impairment. The analysis suggested that decreased neuroglutamate (Glutamate) and γ-aminobutyric acid (GABA) secretion in offspring after PS-NPs intervention was associated with depression. Lastly, intercellular communication revealed alterations in several ligand receptor pathways associated with an increase in astrocytes. In conclusion, spatial transcriptomics reveals that maternal exposure to nanoplastics influences the development of the offspring's hippocampal brain and causes neurotoxicity, which accounts for the offspring's reduction in learning memory function.

Teratological, neurochemical and histomorphic changes in the limbic areas of F1 mice progeny due to co-parental polystyrene nanoplastic exposure

In the present study, co-parental exposure to polystyrene nanoplastics (PS-NPs) elicits profound teratological impacts, including skeletal and visceral malformations, post-natal effects on neonatal growth and neurobehavioral development in F1 progeny. A comprehensive investigation was conducted on Swiss albino mice fetuses, neonates (PND 1-21) and adult mice offsprings (PND 60) following parental exposure during spermatogenesis and oogenesis period, as well as continued maternal exposure during gestation and weaning. The parental mice were administered PS-NPs via oral gavage at low dose (0.2 mg/kg/day) and high dose (1 mg/kg/day). Both male and female parental mice were exposed to PS-NPs for 60 days and 14 days, respectively before mating. After the mating, the pregnant female mice continued to receive PS-NPs treatment during the gestation, till the subsequent weaning period. Our findings revealed that PS-NPs led to significant reductions in growth, and heightened skeletal and visceral anomalies in developing fetuses. Exposure further impaired reflexes in neonatal mice such as grasping, surface righting and negative geotaxis. Moreover, the adult progeny also exhibited learning impairments. Neurodevelopmental assessment unveiled alterations in neurotransmitter levels, antioxidant enzyme activities, and structural changes in key limbic areas such as the cortex, hippocampus, and hypothalamus of adult mice offspring. These alterations included increased vacuolization, vascular dilation, and reduced pyramidal neurons in the hippocampus. Thus, this transgenerational study underscores the detrimental effects of PS-NPs on both prenatal and postnatal development, emphasizing teratological and enduring neurological consequences in the limbic regions of F1 progeny mice brains.

Intestinal Barrier Damage and Growth Retardation Caused by Exposure to Polystyrene Nanoplastics Through Lactation Milk in Developing Mice

Microplastics, defined as plastic fragments smaller than 5 mm, degrade from larger pollutants, with nanoscale microplastic particles presenting significant biological interactions. This study investigates the toxic effects of polystyrene nanoplastics (PS-NPs) on juvenile mice, which were exposed through lactation milk and drinking water at concentrations of 0.01 mg/mL, 0.1 mg/mL, and 1 mg/mL. The results show that PS-NP exposure during lactation and juvenile periods caused delayed weight gain and impaired organ development, particularly in the liver and kidneys, without causing functional abnormalities or toxic injuries. The primary toxicity of PS-NPs was observed in the intestinal tract, including shortened villi, disrupted tight junctions, inhibited epithelial cell proliferation, and oxidative stress responses. These findings highlight the importance of evaluating the developmental toxicity of nanoplastics at environmentally relevant doses.

The role of Sod-2 in different types of neuronal damage and behavioral changes induced by polystyrene nanoplastics in Caenorhabditis elegans

Polystyrene nanoplastics (PS-NPs) have been demonstrated to accumulate in organisms especially from soil and exhibit neurotoxicity. However, the specific mechanisms by which PS-NPs caused neurotoxic effects remain largely unexplored. In this study, we employed PS-NPs with a diameter of 50 nm as the toxicant and used estimated exposure concentrations which are similar to those found in Chinese agricultural soil (i.e., 0, 1, 5 and 10 μg/mL). We found that PS-NPs induced significant neurotoxicity and behavioral damage in nematodes. Taking advantage of neuronal-specific reporter nematodes, we unveiled the order of neuronal damage induced by PS-NPs being DAergic neurons, followed by Achergic neurons and GABAergic neurons. Additionally, PS-NPs significantly reduced the neurotransmitter levels corresponding to these three types of neurons, with the order of reduction being Ach followed by DA and GABA. Moreover, we demonstrated that PS-NPs led to an increase in ROS production, the activation of gst-4 and a decrease in Sod-2 protein content. Furthermore, we unveiled that Sod-2 could suppress the generation of ROS induced by PS-NPs. Then we proved that the pretreatment with mitochondrial ROS scavenger Mitoquinone (Mito Q) was able to alleviate PS-NPs-induced neurotoxic effects and behavioral damage by scavenging ROS and subsequently regulating Sod-2 protein expression. In summary, we have demonstrated for the first time that ROS-mediated reduction of Sod-2 protein plays a crucial role in PS-NPs-induced neurotoxicity and behavioral damage. Furthermore, Mito Q shows potential therapeutic value in alleviating the toxic effects of PS-NPs, providing new insights for the prevention and treatment of PS-NPs-induced neurotoxicity.

Manifestation of polystyrene microplastic accumulation in brain with emphasis on morphometric and histopathological changes in limbic areas of Swiss albino mice

The widespread problem of microplastic (MP) contamination is becoming a major threat to the globe. Although most of the research to date has concentrated on the physiological impacts of MPs exposure, a relatively new field of study is beginning to examine its effects on the behaviour and limbic regions of the brain. In this study, exposure to polystyrene MPs (PS-MPs) for acute and sub-chronic durations negatively affected cognition and induced anxiety-like behaviour in mice. PS-MPs were detected in vital organs of mice, including the brain, which induced neurobehavioural and pathological changes in the limbic system. Furthermore, morphometric analysis revealed a significant decrease in the total cell count in the Dentate Gyrus (DG) and Cornu Ammonis (CA) regions of the hippocampus. Signs of neuronal injury and dystrophic changes were observed in the cortex, amygdala, and hypothalamus, potentially affecting anxiety and fear responses. Our study thus provides insight into the effect of PS-MPs on the neurobiology of the brain's limbic system and related behavioural alterations.

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.

Nasal instillation of polystyrene nanoplastics induce lung injury via mitochondrial DNA release and activation of the cyclic GMP-AMP synthase-stimulator of interferon genes-signaling cascade

Nanoplastics (NPs) are a common type of degraded plastic material associated with adverse health effects such as pulmonary injury. However, the molecular mechanism(s) underlying lung injury as caused by NPs remains uncertain. Thus, we herein investigated the pulmonary toxicity of NPs on RAW264.7 cells and C57BL/6 mice. Our in vitro study indicated that NPs induced oxidative stress, cell death, inflammation, and the activation of the cyclic GMP-AMP synthase (cGAS)-stimulator of interferon genes (STING)-signaling pathway. Mice in our in vivo study displayed significant pulmonary fibrosis, inflammation, apoptosis, necrosis, and excessive double-stranded DNA release into serum and bronchoalveolar lavage fluid. Our mechanistic exploration uncovered cGAS-STING-signaling activation as the leading cause of NPs-induced pulmonary fibrosis. The current study opens an avenue toward elucidating the role of the cGAS-STING-signaling pathway in NPs-induced pulmonary injury.

Vertebrate response to microplastics, nanoplastics and co-exposed contaminants: Assessing accumulation, toxicity, behaviour, physiology, and molecular changes

Pollution from microplastics (MPs) and nanoplastics (NPs) has gained significant public attention and has become a serious environmental problem worldwide. This review critically investigates MPs/NPs' ability to pass through biological barriers in vertebrate models and accumulate in various organs, including the brain. After accumulation, these particles can alter individuals' behaviour and exhibit toxic effects by inducing oxidative stress or eliciting an inflammatory response. One major concern is the possibility of transgenerational harm, in which toxic consequences are displayed in offspring who are not directly exposed to MPs/NPs. Due to their large and marked surface hydrophobicity, these particles can easily absorb and concentrate various environmental pollutants, which may increase their toxicity to individuals and subsequent generations. This review systematically provides an analysis of recent studies related to the toxic effects of MPs/NPs, highlighting the intricate interplay between co-contaminants in vitro and in vivo. We further delve into mechanisms of MPs/NPs-induced toxicity and provide an overview of potential therapeutic approaches to lessen the negative effects of these MPs/NPs. The review also emphasizes the urgency of future studies to examine the long-term effects of chronic exposure to MPs/NPs and their size- and type-specific hazardous dynamics, and devising approaches to safeguard the affected organisms.

Combined effect of polystyrene nanoplastic and di-n-butyl phthalate on testicular health of male Swiss albino mice: analysis of sperm-related parameters and potential toxic effects

Plastics, especially polystyrene nanoplastic particles (PSNPs), are known for their durability and absorption properties, allowing them to interact with environmental pollutants such as di-n-butyl phthalate (DBP). Previous research has highlighted the potential of these particles as carriers for various pollutants, emphasizing the need to understand their environmental impact comprehensively. This study focuses on the subchronic exposure of male Swiss albino mice to PSNP and DBP, aiming to investigate their reproductive toxicity between these pollutants in mammalian models. The primary objective of this study is to examine the reproductive toxicity resulting from simultaneous exposure to PSNP and DBP in male Swiss albino mice. The study aims to analyze sperm parameters, measure antioxidant enzyme activity, and conduct histopathological and morphometric examinations of the testis. By investigating the individual and combined effects of PSNP and DBP, the study seeks to gain insights into their impact on the reproductive profile of male mice, emphasizing potential synergistic interactions between these environmental pollutants. Male Swiss albino mice were subjected to subchronic exposure (60 days) of PSNP (0.2 mg/m, 50 nm size) and DBP (900 mg/kg bw), both individually and in combination. Various parameters, including sperm parameters, antioxidant enzyme activity, histopathological changes, and morphometric characteristics of the testis, were evaluated. The Johnsen scoring system and histomorphometric parameters were employed for a comprehensive assessment of spermatogenesis and testicular structure. The study revealed non-lethal effects within the tested doses of PSNP and DBP alone and in combination, showing reductions in body weight gain and testis weight compared to the control. Individual exposures and the combination group exhibited adverse effects on sperm parameters, with the combination exposure demonstrating more severe outcomes. Structural abnormalities, including vascular congestion, Leydig cell hyperplasia, and the extensive congestion in tunica albuginea along with both ST and Leydig cell damage, were observed in the testis, underscoring the reproductive toxicity potential of PSNP and DBP. The Johnsen scoring system and histomorphometric parameters confirmed these findings, providing interconnected results aligning with observed structural abnormalities. The study concludes that simultaneous exposure to PSNP and DBP induces reproductive toxicity in male Swiss albino mice. The combination of these environmental pollutants leads to more severe disruptions in sperm parameters, testicular structure, and antioxidant defense mechanisms compared to individual exposures. The findings emphasize the importance of understanding the interactive mechanisms between different environmental pollutants and their collective impact on male reproductive health. The use of the Johnsen scoring system and histomorphometric parameters provides a comprehensive evaluation of spermatogenesis and testicular structure, contributing valuable insights to the field of environmental toxicology.