Oral exposure to polyethylene microplastics induces inflammatory and metabolic changes and promotes fibrosis in mouse liver

Ingestion of polyethylene terephthalate microplastic water contaminants by Xenopus laevis tadpoles negatively affects their resistance to ranavirus infection and antiviral immunity

Small plastic debris (0.1 μm-5 mm) or microplastics (MPs) have become major pollutants of aquatic ecosystems worldwide and studies suggest that MPs exposure can pose serious threats to human and wildlife health. However, to date the potential biological impacts of MPs accumulating in low amount in tissues during early life remains unclear. Here, for a more realistic assessment, we have used environmentally representative, mildly weathered, polyethylene terephthalate microplastics (PET MPs), cryomilled (1-100 μm) and fluorescently labelled. We leveraged the amphibian Xenopus laevis tadpoles as an animal model to define the biodistribution of PET MPs and determine whether exposure to PET MPs induce perturbations of antiviral immunity. Exposure to PET MPs for 1-14 days resulted in detectable PET MPs biodistribution in intestine, gills, liver, and kidney as determined by fluorescence microscopy on whole mount tissues. PET MPs accumulation rate in tissues was further evaluated via a novel in situ enzymatic digestion and subsequent filtration using silicon nanomembranes, which shows that PET MPs rapidly accumulate in tadpole intestine, liver and kidneys and persist over a week. Longer exposure (1 month) of tadpoles to relatively low concentration of PET MPs (25 μg/ml) significantly increased susceptibility to viral infection and altered innate antiviral immunity without inducing overt inflammation. This study provides evidence that exposure to MPs negatively impact immune defenses of aquatic vertebrates.

Potential mechanisms of aortic medial degeneration promoted by co-exposure to microplastics and lead

Microplastics (MPs) have attracted widespread attention because they can lead to combined toxicity by adsorbing heavy metals from the environment. Exposure to lead (Pb), a frequently adsorbed heavy metal by MPs, is common. In the current study, the coexistence of MPs and Pb was assessed in human samples. Then, mice were used as models to examine how co-exposure to MPs and Pb promotes aortic medial degeneration. The results showed that MPs and Pb co-exposure were detected in patients with aortic disease. In mice, MPs and Pb co-exposure promoted the damage of elastic fibers, loss of vascular smooth muscle cells (VSMCs), and release of inflammatory factors. In vitro cell models revealed that co-exposure to MPs and Pb induced excessive reactive oxygen species generation, impaired mitochondrial function, and triggered PANoptosome assembly in VSMCs. These events led to PANoptosis and inflammation through the cAMP/PKA-ROS signaling pathway. However, the use of the PKA activator 8-Br-cAMP or mitochondrial ROS scavenger Mito-TEMPO improved, mitochondrial function in VSMCs, reduced cell death, and inhibited inflammatory factor release. Taken together, the present study provided novel insights into the combined toxicity of MPs and Pb co-exposure on the aorta.

Co-exposure of polyvinyl chloride microplastics with cadmium promotes nonalcoholic fatty liver disease in female ducks through oxidative stress and glycolipid accumulation

A recently discovered environmental contaminant, microplastics (MP) are capable of amassing within the body and pose a grave threat to the health of both humans and animals. It is widely acknowledged that the combination of cadmium (Cd), a hazardous heavy metal, and microplastics produces synergistic deleterious effects. Nevertheless, the mechanism by which co-exposure to polyvinyl chloride microplastics (PVC-MP) and Cd damages the liver of avian females is unknown. Globally prevalent and the subject of extensive research in mammals, nonalcoholic fatty liver disease (NAFLD) is a chronic liver condition. However, the mechanisms underlying injury to the avian digestive system caused by NAFLD remain unknown. Two months of co-exposure to Cd and PVC-MPs, pure water, solitary Cd exposure, single microplastics exposure, and pure water were administered to female Muscovy ducks in this study. The objective of this research was to examine whether the co-exposure of duck liver to PVC-MPs and Cd-induced oxidative stress resulted in NAFLD and subsequent apoptosis of hepatic cells. The study's findings showed that hepatocyte shape and functional activity were negatively impacted by PVC-MP and Cd buildup in liver tissues. Reduced liver organ coefficients, increased alanine aminotransferase (ALT) content, and ultrastructural damage to hepatocyte nuclei and mitochondria are indicators of this. These results point to a possible impairment in liver function. phosphoenolpyruvate carboxykinase 1 (PCK1) deficiency activates the protein kinase B/phosphatidylinositol 3-kinase (PI3K/AKT) pathway in the livers of female reproductive ducks that have been damaged by oxidative stress. This stimulation induces lipid deposition, fibrosis, and glycogen accumulation, which ultimately results in hepatocyte apoptosis. In summary, our research provides evidence that PVC-MPs cause oxidative harm to the liver, which subsequently results in fibrosis of liver tissue, hepatic glucolipid metabolism, and ultimately apoptosis.

The size-dependence and reversibility of polystyrene nanoplastics-induced hepatic pyroptosis in mice through TXNIP/NLRP3/GSDMD pathway

As emerging environmental contaminants, nanoplastics (NPs) are progressively accumulating in terrestrial and aquatic ecosystems worldwide, posing a potential threat to human health. The liver is considered as one of the primary organs targeted by NPs accumulation in living organisms. However, there remains a large knowledge gap concerning NPs-induced hepatotoxicity. In this study, we examined the impact of chronic exposure to environmentally relevant doses of polystyrene (PS) NPs on hepatic pyroptosis in mice. The results demonstrated that both particle sizes of PS-NPs (100 nm and 500 nm) significantly triggered pyroptosis in the mouse liver, as evidenced by the upregulation of GSDMD-N protein levels; moreover, this pyroptotic effect induced by 100 nm PS-NPs was more pronounced compared to that of 500 nm PS-NPs. Mechanistically, exposure to 100 nm and 500 nm PS-NPs resulted in an upregulation of TXNIP protein expression, thereby activating NLRP3 inflammasome and subsequently inducing inflammatory responses and pyroptosis. Notably, following the termination of PS-NPs exposure and a subsequent recovery period of 50 days, PS-NPs-mediated inflammation and pyroptosis via TXNIP/NLRP3 pathway were effectively ameliorated, even returning to levels close to the baseline. Collectively, our findings provide novel evidence for the size-dependence and reversibility of NPs-induced hepatic pyroptosis through TXNIP/NLRP3/GSDMD pathway in vivo.

Plastic compounds and liver diseases: Whether bisphenol A is the only culprit

Plastics, while providing modern conveniences, have become an inescapable source of global concern due to their role in environmental pollution. Particularly, the focus on bisphenol A (BPA) reveals its biohazardous nature and association with liver issues, specifically steatosis. However, research indicates that BPA is just one facet of the problem, as other bisphenol analogues, microplastics, nanoplastics and additional plastic derivatives also pose potential risks. Notably, BPA is implicated in every stage of non-alcoholic fatty liver disease (NAFLD) onset and progression, surpassing hepatitis B virus as a primary cause of chronic liver disease worldwide. As plastic contamination tops the environmental contaminants list, urgent action is needed to assess causative factors and mitigate their impact. This review delves into the molecular disruptions linking plastic pollutant exposure to liver diseases, emphasizing the broader connection between plastics and the rising prevalence of NAFLD.

A novel tiRNA-Glu-CTC induces nanoplastics accelerated vascular smooth muscle cell phenotypic switching and vascular injury through mitochondrial damage

Nanoplastics pose several health hazards, especially vascular toxicity. Transfer RNA-derived small RNAs (tsRNAs) are novel noncoding RNAs associated with different pathological processes. However, their biological roles and mechanisms in aberrant vascular smooth muscle cell (VSMC) plasticity and vascular injury are unclear. This study investigated the potent effects of tsRNAs on vascular injury induced by short- and long-term exposure to polystyrene nanoplastics (PS-NPs). Mice were exposed to PS-NPs (100 nm) at different doses (10-100 μg/mL) for 30 or 180 days. High-throughput sequencing was used to analyze tsRNA expression patterns in arterial tissues obtained from an in vivo model. Additionally, quantitative real-time polymerase chain reaction, fluorescent in situ hybridization assays, and dual-luciferase reporter assays were performed to measure the expression and impact of tiRNA-Glu-CTC on VSMCs exposed to PS-NPs. Short-term (≥50 μg/mL, moderate concentration) and long-term (≥10 μg/mL, low concentration) PS-NP exposure induced vascular injury in vivo. Cellular experiments showed that the moderate concentration of PS-NPs induced VSMC phenotypic switching, whereas a high concentration of PS-NPs (100 μg/mL) promoted VSMC apoptosis. PS-NP induced severe mitochondrial damage in VSMCs, including overexpression of reactive oxygen species, accumulation of mutated mtDNA, and dysregulation of genes related to mitochondrial synthesis and division. Compared with the control group, 13 upregulated and 12 downregulated tRNA-derived stress-induced RNAs (tiRNAs) were observed in the long-term PS-NP (50 μg/mL) exposure group. Bioinformatics analysis indicated that differentially expressed tiRNAs targeted genes that were involved in vascular smooth muscle contraction and calcium signaling pathways. Interestingly, tiRNA-Glu-CTC was overexpressed in vivo and in vitro following PS-NP exposure. Functionally, the tiRNA-Glu-CTC inhibitor mitigated VSMC phenotypic switching and mitochondrial damage induced by PS-NP exposure, whereas tiRNA-Glu-CTC mimics had the opposite effect. Mechanistically, tiRNA-Glu-CTC mimics induced VSMC phenotypic switching by downregulating Cacna1f expression. PS-NP exposure promoted VSMC phenotypic switching and vascular injury by targeting the tiRNA-Glu-CTC/Cacna1f axis.

The potential impacts of micro-and-nano plastics on various organ systems in humans

Humans are exposed to micro-and-nano plastics (MNPs) through various routes, but the adverse health effects of MNPs on different organ systems are not yet fully understood. This review aims to provide an overview of the potential impacts of MNPs on various organ systems and identify knowledge gaps in current research. The summarized results suggest that exposure to MNPs can lead to health effects through oxidative stress, inflammation, immune dysfunction, altered biochemical and energy metabolism, impaired cell proliferation, disrupted microbial metabolic pathways, abnormal organ development, and carcinogenicity. There is limited human data on the health effects of MNPs, despite evidence from animal and cellular studies. Most of the published research has focused on specific types of MNPs to assess their toxicity, while other types of plastic particles commonly found in the environment remain unstudied. Future studies should investigate MNPs exposure by considering realistic concentrations, dose-dependent effects, individual susceptibility, and confounding factors.