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Polystyrene Nanoplastics Exacerbate HFD-induced MASLD by Reducing Cathepsin Activity and Triggering Large Vacuole Formation via Impaired Lysosomal Acidification
Summary
Researchers found that polystyrene nanoplastics, when combined with a high-fat diet in mice, significantly worsened fatty liver disease symptoms compared to either factor alone. The nanoplastics impaired the function of lysosomes, the cell's recycling centers, by preventing proper acidification and reducing enzyme activity. The study suggests that nanoplastic exposure could amplify diet-related liver problems by interfering with how cells process and break down fats.
Environmental nanoplastics (NPs) have harmful effects on health. This study investigated the effects of polystyrene (PS) NPs on steatosis and fatty liver disease. PS-NP oral administration, in conjunction with a high-fat diet (HFD), synergistically exacerbated the symptoms of steatosis in mice, leading to increased alanine transaminase, aspartate aminotransferase, and cholesterol levels; no effects were observed with PS-NPs on a normal chow diet. Transcriptome analysis unveiled that PS-NPs interfered with actin organization, cell-cell adhesion, PPAR signaling, and lipid metabolism. In HepaRG cells, PS-NPs rapidly entered by inducing actin rearrangement, resulting in the formation of numerous small cytoplasmic vesicles. This treatment led to an augmented number of acidic organelles, leading to development and buildup of large vacuoles, indicative of enlarged pre-lysosomal and lysosomal compartments. PS-NP exposure hampered p62 degradation, leading to LC3B accumulation and decreased cathepsin B and D activity. Additionally, PS-NP exposure resulted in accumulation of lipid droplets and elevated expression of lipogenesis-, transport-, and storage-related genes. These findings suggest that excessive endocytosis driven by PS-NPs worsens MASLD in HFD through accumulation of lysosomes and large vacuoles with reduced cathepsin activity.
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