The presence of nanoplastics in aquatic environments is a global problem. Accumulating evidence shows that nanoplastics can accumulate in fish and influence internal organs. However, it is still unknown if nanoplastics can impair skin cells (keratinocytes and ionocytes), which play critical roles in maintaining body fluid homeostasis. In the present study, zebrafish embryos were exposed to polystyrene nanoplastics (PS-NPs; 25 nm in size, at 0, 10, 25, and 50 mg/L) for 96 h to test the effects of PS-NPs on skin functions. After exposure to 50 mg/L, the survival rate, ion (Na⁺, K⁺, and Ca²⁺) contents, and acid/ammonia excretion by skin cells of embryos significantly declined. The apical structure of skin keratinocytes was damaged at 10, 25, and 50 mg/L. The number and mitochondrial activity of ionocytes were reduced at 25 and 50 mg/L. Reactive oxygen species (ROS) levels indicated by CellROX staining showed that both ionocytes and keratinocytes were under oxidative stress. PS-NPs reduced the mRNA expression of antioxidant genes (sod1, sod2, cat, and gpx1a), and promoted apoptosis-related genes (casp3a). Taken together, this study suggests that PS-NPs might suppress antioxidative reactions and induce oxidative stress, leading to mitochondrial damage and cell death of ionocytes, eventually impairing skin functions including ion uptake, pH regulation, and ammonia excretion.

水生环境中纳米塑料的存在是一个全球性问题。越来越多的证据表明，纳米塑料可以在鱼体内积累并影响内脏。然而，目前尚不清楚纳米塑料是否会损害皮肤细胞（角质形成细胞和离子细胞），而这些细胞在维持体液稳态方面发挥着关键作用。在本研究中，斑马鱼胚胎暴露于聚苯乙烯纳米塑料（PS-NPs；尺寸为 25 nm，浓度为 0、10、25 和 50 mg/L）中 96 小时，以测试 PS-NPs 对皮肤功能的影响。暴露于 50 mg/L 后，存活率、离子（Na ⁺、K ⁺和 Ca ²⁺) 含量，胚胎皮肤细胞的酸/氨排泄量显着下降。皮肤角质形成细胞的顶端结构在 10、25 和 50 mg/L 时受损。离子细胞的数量和线粒体活性在 25 和 50 mg/L 时降低。CellROX 染色显示的活性氧 (ROS) 水平显示离子细胞和角质形成细胞都处于氧化应激状态。PS-NPs 降低抗氧化基因（sod1、sod2、cat和gpx1a）的 mRNA 表达，并促进凋亡相关基因（casp3a）。综上所述，本研究表明 PS-NPs 可能抑制抗氧化反应并诱导氧化应激，导致线粒体损伤和离子细胞死亡，最终损害皮肤功能，包括离子摄取、pH 调节和氨排泄。