Vitamin D modulation of brain-gut-virome disorder caused by polystyrene nanoplastics exposure in zebrafish (Danio rerio)

Trehalose Acts as a Mediator: Imbalance in Brain Proteostasis Induced by Polystyrene Nanoplastics via Gut Microbiota Dysbiosis during Early Life

As an emerging contaminant, nanoplastics have evolved into a global ecological issue. Studies have shown that nanoplastics induce neurotoxicity across species, however, the causal mechanism remains unknown. This study aimed to explore the mechanism underlying the neurotoxicity caused by polystyrene nanoplastics (PS-NPs) via microbiota-gut-brain axis in immature mice, which serve as a model of infants and young children who are at higher exposure risk to NPs. The results indicated that while only a minority of PS-NPs reached the brain after exposure, they still had significant neurotoxic effects, as reflected by abnormalities in behavior, biochemical marker levels and histopathology. Proteomics and quantification analyses revealed that a proteostasis imbalance mediated by lysosomal and proteasome dysfunction in the brain is the key reason for the induced neurotoxicity. Further, we confirmed the indirect role of gut microbiota in the neurotoxicity induced by PS-NPs through 16S rDNA analyses and fecal microbiota transplantation. Crucial bacterial species such as Eubacterium coprostanoligenes potentially act as indicators for gut dysbiosis after PS-NPs exposure. Notably, we first estimated the indirect effect of gut microbiota on neurotoxicity attributed to PS-NPs in immature mice as 39.20% by high-dimensional mediation analysis. Trehalose was identified as a mediator connecting the gut microbiota and the brain, and the crucial role of trehalose supplementation was highlighted in remodeling the brain proteostasis to alleviate the neurotoxicity in immature mice. These findings are expected to contribute to a deeper understanding of the risk assessment and health protection of the nervous system from exposure to PS-NPs early in life.

Polystyrene nanoplastics exposure trigger cognitive impairment mitigated by luteolin modulated glucose-6-phosphate dehydrogenase/glutathione-dependent pathway

The neurotoxicological consequences of chronic exposure to polystyrene nanoplastics (PSNPs) at environmentally relevant concentrations remain poorly understood, particularly their impact on hippocampal neurons dysfunction. In this study, a mouse model co-exposed to PSNPs and/or luteolin (LUT) was replicated by intraperitoneal injection to investigate the mechanism and effective treatment of PSNPs induced striatal neurodegeneration. Here, we elucidated that PSNPs exposure induced striatal injury characterized by neuronal disorganization and mitochondrial dysfunction in vivo and in vitro. Notably, PSNPs triggered oxidative dysregulation and iron accumulation by enhancing antioxidant enzyme activity and suppressing lipid peroxidation, leading to ferroptosis and neuroinflammation. Additionally, PSNPs exposure induced a decrease in glycolysis and tricarboxylic acid (TCA) cycle imbalance by disrupting G6PD/glutathione-dependent pathway, leading to an imbalance in cellular energy metabolism. Our findings highlighted the role of the Piezo1/CaN/NFAT1 axis in PSNPs-induced ER Ca2 + homeostasis imbalance, which was effectively inhibited by LUT. Notably, LUT alleviated the susceptibility to striatal ferroptosis induced by PSNPs via the G6PD/glutathione axis. Collectively, our study provides critical insights into the neurotoxic mechanisms of PSNPs and establishes LUT as a agent against PSNPs-induced neurodegeneration. These findings underscore the urgent need for environmental regulation of nanoplastics and offer potential strategies for combating their health effects.

Lactic acid bacteria reduce polystyrene micro- and nanoplastics-induced toxicity through their bio-binding capacity and gut environment repair ability

Microplastics and nanoplastics (MNPs) are emerging environmental contaminants that have received significant attention in recent years. Currently, there are more studies on the toxic effects of MNPs exposure on animals (especially aquatic organisms and mammals), but data on the reduction of toxic effects caused by MNPs exposure are still very limited. Lactic acid bacteria (LAB), recognized as safe food-grade microorganisms, possess the capability to bioconjugate harmful substances. In this experiment, we chose lactic acid bacteria (LAB) with different binding capacities to MNPs in vitro to intervene in MNPs-exposed mice to investigate the reducing effect on the toxicity caused by MNPs exposure. Our study showed that LAB with a high intercalation capacity with MNPs in vitro were more effective in alleviating the toxicity caused by MNPs exposure. Notably, Lactobacillus plantarum DT22, despite its low inter-adsorption with MNPs, played a pivotal role in upregulating the relative expression of tight junction proteins and modulating the intestinal microbiota. Thus, LAB strains' mitigation of MNPs toxicity extends beyond bio-binding; their capacity to repair the damaged gut environment is also crucial. LAB strains are proposed as a dietary intervention to reduce MNPs-induced toxicity.

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.

Polystyrene microplastics induce depression-like behavior in zebrafish via neuroinflammation and circadian rhythm disruption

Polystyrene microplastics (PS-MPs) are widespread pollutants in aquatic environments that accumulate in various organs, including the brain, raising concerns about their neurotoxic effects. This study exposed zebrafish to environmentally relevant concentrations (25 and 250 μg/L) of PS-MPs for 40 days to investigate their impact on neurobehavior and underlying mechanisms. Results revealed that PS-MPs induced depression-like behaviors in zebrafish, characterized by reduced exploration, decreased locomotor activity, and altered social interaction. Histological analyses of brain tissue demonstrated PS-MPs-induced neuropathological changes, including perinuclear vacuolation and reduced Nissl bodies. Additionally, PS-MPs triggered neuroinflammation, evidenced by upregulated pro-inflammatory cytokines (il-6, il-1β), and disrupted the circadian rhythm, leading to altered expression of key clock genes (per1b, per2, per3) and cryptochrome genes (cry1a, cry2). Furthermore, PS-MPs exposure significantly altered neurotransmitter levels, decreasing dopamine, serotonin, norepinephrine, acetylcholine, tyrosine, and tryptophan. In vitro experiments using HMC3 microglia cells confirmed that PS-MPs induced microglial activation, morphological changes, and dysregulated gene expression related to inflammation and circadian rhythm. These findings provide compelling evidence that PS-MPs induce depression-like behaviors in zebrafish through mechanisms involving neuroinflammation, circadian rhythm disruption, and neurotransmitter imbalances, highlighting the potential ecological risks of PS-MPs and contributing to our understanding of the neurotoxicity of microplastics.

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.

Pulmonary Flora-Derived Lipopolysaccharide Mediates Lung-Brain Axis through Activating Microglia Involved in Polystyrene Microplastic-Induced Cognitive Dysfunction

Microplastics (MPs) have been detected in the atmospheric and the human respiratory system, indicating that the respiratory tract is a significant exposure route for MPs. However, the effect of inhaled MPs on cognitive function has not been adequately studied. Here, a C57BL/6 J mouse model of inhalation exposure to polystyrene MPs (PS-MPs, 5 µm, 60 d) is established by intratracheal instillation. Interestingly, in vivo fluorescence imaging and transmission electron microscopy reveal that PS-MPs do not accumulate in the brain. However, behavioral experiments shows that cognitive function of mice is impaired, accompanied by histopathological damage of lung and brain tissue. Transcriptomic studies in hippocampal and lung tissue have demonstrated key neuroplasticity factors as well as cognitive deficits linked to lung injury, respectively. Mechanistically, the lung-brain axis plays a central role in PS-MPs-induced neurological damage, as demonstrated by pulmonary flora transplantation, lipopolysaccharide (LPS) intervention, and cell co-culture experiments. Together, inhalation of PS-MPs reduces cognitive function by altering the composition of pulmonary flora to produce more LPS and promoting M1 polarization of microglia, which provides new insights into the mechanism of nerve damage caused by inhaled MPs and also sheds new light on the prevention of neurotoxicity of environmental pollutants.

Black phosphorus quantum dots induced neurotoxicity, intestinal microbiome and metabolome dysbiosis in zebrafish (Danio rerio)

The potential toxicity of BPQDs has received considerable attention due to their increasing use in biomedical applications. In this study, the toxicity of BPQDs at concentrations of 5 μg/mL, 50 μg/mL, and 500 μg/mL on the brain-gut axis was assessed in zebrafish. Following 35 days of exposure, the neurotransmitter, locomotor behavior, gut barrier (physical barrier, chemical barrier, and microbial barrier), and gut content metabolism in zebrafish were evaluated. The results indicated that BPQDs induced the locomotor behavior abnormalities, inhibited acetylcholinesterase activity, induced dopaminase activity, and promoted apoptosis in zebrafish brain tissue. Meanwhile, BPQDs caused damage to the physical and chemical barriers in zebrafish intestinal tissue, which increased the permeability of the intestinal mucosa, and induced oxidative stress and apoptosis. The gut microbiota was analyzed by 16S rRNA gene sequencing. The results showed that BPQDs caused dysbiosis of the gut microbiota, resulting in decreased diversity. Specifically, the relative abundance of Firmicutes, Bacteroidetes, and Actinobacteria decreased, while the relative abundance of Proteobacteria and Clostriobacteria increased. At the genus level, the high concentration BPQDs showed a significant increase in Cetobacterium, Pleisionomas, Aeromonas, and other bacteria. Bioinformatic analysis revealed a correlation between the relative abundance of the gut microbiota and antioxidant levels, immune response, and apoptosis. Statistical analysis of the metabolomic revealed significant perturbations in several metabolic pathways, including amino acid, lipid, nucleotide, and energy metabolism. In addition, correlation analysis between microbiota and metabolism confirmed that gut microbiota dysbiosis was closely associated with metabolic dysfunction. The histopathologic injury supported the changes in biomarkers and the expression of related marker genes in the gut-brain axis, indicating the communication between the gut peripheral nerves and the CNS. The results indicate that BPQDs induce gut microbiota dysbiosis, disrupt metabolic function, and induce neurotoxicity, probably by disrupting the homeostasis of the microbiota-gut-brain axis. In summary, this study demonstrates the effects of BPQDs on physiological changes within the zebrafish brain-gut axis and provides valuable data for assessing the toxicological risks of BPQDs in aquatic ecosystems.

Innovative mechanisms of micro- and nanoplastic-induced brain injury: Emphasis on the microbiota-gut-brain axis

Micro- and nanoplastics (MNPs), emerging environmental pollutants, infiltrate marine, terrestrial, and freshwater systems via diverse pathways, culminating in their accumulation in the human body through food chain transmission, posing potential health risks. Researches have demonstrated that MNPs disrupt gut microbiota equilibrium and compromise intestinal barrier integrity, as well as traverse the blood-brain barrier, leading to brain damage. Moreover, the complex interaction between the gut and the nervous system, facilitated by the "gut-brain axis," indicates an additional pathway for MNPs-induced brain damage. This has intensified scientific interest in the intercommunication between MNPs and the gut-brain axis. While existing studies have documented microbial imbalances and metabolic disruptions subsequent to MNPs exposure, the precise mechanisms by which the microbiota-gut-brain axis contributes to MNPs-induced central nervous system damage remain unclear. This review synthesizes current knowledge on the microbiota-gut-brain axis, elucidating the pathogenesis of MNPs-induced gut microbiota dysbiosis and its consequent brain injury. It emphasizes the complex interrelation between MNPs and the microbiota-gut-brain axis, advocating for the gut microbiota as a novel therapeutic target to alleviate MNP-induced brain harm.

Mitigating Dietary Microplastic Accumulation and Oxidative Stress Response in European Seabass (Dicentrarchus labrax) Juveniles Using a Natural Microencapsulated Antioxidant

Aquafeed's contamination by microplastics can pose a risk to fish health and quality since they can be absorbed by the gastrointestinal tract and translocate to different tissues. The liver acts as a retaining organ with the consequent triggering of oxidative stress response. The present study aimed to combine the use of natural astaxanthin with natural-based microcapsules to counteract these negative side effects. European seabass juveniles were fed diets containing commercially available fluorescent microplastic microbeads (1-5 μm; 50 mg/kg feed) alone or combined with microencapsulated astaxanthin (AX) (7 g/kg feed; tested for half or whole feeding trial-30 or 60 days, respectively). Fish from the different dietary treatments did not evidence variations in survival and growth performance and did not show pathological alterations at the intestinal level. However, the microplastics were absorbed at the intestinal level with a consequent translocation to the liver, leading, when provided solely, to sod1, sod2, and cat upregulation. Interestingly, the dietary implementation of microencapsulated AX led to a mitigation of oxidative stress. In addition, the microcapsules, due to their composition, promoted microplastic coagulation in the fish gut, limiting their absorption and accumulation in all the tissues analyzed. These results were supported by in vitro tests, which demonstrated that the microcapsules promoted microplastic coagula formation too large to be absorbed at the intestinal level and by the fact that the coagulated microplastics were released through the fish feces.

Interactions between intestinal microbiota and metabolites in zebrafish larvae exposed to polystyrene nanoplastics: Implications for intestinal health and glycolipid metabolism

Previous studies have shown the harmful effects of nanoscale particles on the intestinal tracts of organisms. However, the specific mechanisms remain unclear. Our present study focused on examining the uptake and distribution of polystyrene nanoplastics (PS-NPs) in zebrafish larvae, as well as its toxic effects on the intestine. It was found that PS-NPs, marked with red fluorescence, primarily accumulated in the intestine section. Subsequently, zebrafish larvae were exposed to normal PS-NPs (0.2-25 mg/L) over a critical 10-day period for intestinal development. Histopathological analysis demonstrated that PS-NPs caused structural changes in the intestine, resulting in inflammation and oxidative stress. Additionally, PS-NPs disrupted the composition of the intestinal microbiota, leading to alterations in the abundance of bacterial genera such as Pseudomonas and Aeromonas, which are associated with intestinal inflammation. Metabolomics analysis showed alterations in metabolites that are primarily involved in glycolipid metabolism. Furthermore, MetOrigin analysis showed a significant correlation between bacterial flora (Pedobacter and Bacillus) and metabolites (D-Glycerate 2-phosphate and D-Glyceraldehyde 3-phosphate), which are related to the glycolysis/gluconeogenesis pathways. These findings were further validated through alterations in multiple biomarkers at various levels. Collectively, our data suggest that PS-NPs may impair the intestinal health, disrupt the intestinal microbiota, and subsequently cause metabolic disorders.

Dietary lipid supplementation alleviated the impacts of polystyrene nanoplastic exposure in Litopenaeus vannamei

The widespread occurrence of nanoplastic (NP) pollution in the environment is a growing concern, and its presence poses a potential threat to cultured aquatic animals. Previously, we found that NPs can significantly affect the lipid metabolism of shrimp. However, relevant reports about the effects of increasing dietary lipid levels on NP toxicity are lacking. Therefore, we explored the effects of dietary supplementation with different lipid levels on the growth and lipid metabolism of Pacific white shrimp (Litopenaeus vannamei). We cultured L. vannamei at three dietary lipid levels (3 %, 6 %, and 9 %) and three NP concentrations (0, 1, and 3 mg/L) for 2 months. We evaluated the effects of lipid levels on growth indexes, hepatopancreas morphological structure, lipid metabolism-related enzyme activity, and gene expression of the shrimp. The results showed that as lipid intake increased, the survival rate, body weight growth rate, and hepatosomatic ratio of the shrimp increased while the feed conversion rate decreased. Additionally, the crude protein and crude lipid contents increased, whereas the moisture and ash contents did not change much. We found that the morphological structure of the hepatopancreas was seriously damaged in the 3 mg/L NPs and 3 % dietary lipid group. Finally, lipid metabolism-related enzyme activities and gene expression levels increased with increased dietary lipid levels. Together, these results suggest that increasing dietary lipid content can improve shrimp growth and alleviate lipid metabolism disorders caused by NPs. This study is the first to show that nutrition regulation can alleviate the toxicity of NPs, and it provides a theoretical basis for the green and healthy culture of L. vannamei.

From cradle to grave: Deciphering sex-specific disruptions of the nervous and reproductive systems through interactions of 4-methylbenzylidene camphor and nanoplastics in adult zebrafish

4-methylbenzylidene camphor (4-MBC) and micro/nanoplastics (MNPs) are common in personal care and cosmetic products (PCCPs) and consumer goods; however, they have become pervasive environmental contaminants. MNPs serve as carriers of 4-MBC in both PCCPs and the environment. Our previous study demonstrated that 4-MBC induces estrogenic effects in zebrafish larvae. However, knowledge gaps remain regarding the sex- and tissue-specific accumulation and potential toxicities of chronic coexposure to 4-MBC and MNPs. Herein, adult zebrafish were exposed to environmentally realistic concentrations of 4-MBC (0, 0.4832, and 4832 μg/L), with or without polystyrene nanoplastics (PS-NPs; 50 nm, 1.0 mg/L) for 21 days. Sex-specific accumulation was observed, with higher concentrations in female brains, while males exhibited comparable accumulation in the liver, testes, and brain. Coexposure to PS-NPs intensified the 4-MBC burden in all tested tissues. Dual-omics analysis (transcriptomics and proteomics) revealed dysfunctions in neuronal differentiation, death, and reproduction. 4-MBC-co-PS-NP exposure disrupted the brain histopathology more severely than exposure to 4-MBC alone, inducing sex-specific neurotoxicity and reproductive disruptions. Female zebrafish exhibited autism spectrum disorder-like behavior and disruption of vitellogenesis and oocyte maturation, while male zebrafish showed Parkinson's-like behavior and spermatogenesis disruption. Our findings highlight that PS-NPs enhance tissue accumulation of 4-MBC, leading to sex-specific impairments in the nervous and reproductive systems of zebrafish.