The ubiquitous presence of microplastics and their marine ecotoxicity are major public concerns. Microplastics are ingested accidentally by the marine fauna or are taken up indirectly through the food chain. These particles can accumulate in cells and tissues and affect the normal biological functions of organisms, including their defense mechanisms. There is limited information available about the response of immune cells to microplastics; the degree of uptake by the cells, the response of different organs or the impact of environmental concentrations of microplastic are matters that remain unclear. Moreover, very little is known about the toxicity of different polymer types. This study aimed to shed light on the physical impact of small microplastics (1–5 μm) on cells from Atlantic salmon. Immune cells from intestine, blood, and head kidney were exposed to green fluorescent polyethylene microplastic (PE-MP), yellow fluorescent polystyrene microplastic (PS-MP) and both. High (50 mg/L), medium (5 mg/L), and low (0.05 mg/L) concentrations were tested for 1, 24, 48, and 72 h to study cell mortality and microplastic uptake. Quantitative data of microplastic uptake by fish immune cells were obtained for the first time by imaging flow cytometry. Salmon immune cells showed a relatively low ability to phagocytose microplastics. Less than 6% of the cells ingested the particles after 48 h of exposure to high concentrations. Cells also phagocytosed microplastics at low concentrations although at low rates (<0.1%). PE-MPs was phagocytosed by higher percentage of cells compared to PS-MPs and the former bioaccumulated in time while the latter decreased over time. However, each cell generally phagocytosed more PS-MPs particles than PE-MPs. Cells from different tissues showed different responses to the microplastic polymers. In conclusion, this study shows that immune cells of Atlantic salmon can phagocytose microplastics, and the impact is dependent on the microplastic type. PE-MPs, the most abundant polymer in the oceans and a widely used plastic in salmon aquaculture, was more easily taken up than PS-MPs. Furthermore, the study demonstrates how imaging flow cytometry can be applied in microplastics research.

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大西洋鲑鱼 (Salmo salar L.) 免疫细胞对荧光微塑料的摄取

微塑料的普遍存在及其海洋生态毒性是公众关注的主要问题。微塑料被海洋动物意外摄入或通过食物链间接摄入。这些颗粒会在细胞和组织中积聚并影响生物体的正常生物功能，包括它们的防御机制。关于免疫细胞对微塑料的反应的信息有限；细胞吸收的程度、不同器官的反应或微塑料的环境浓度的影响尚不清楚。此外，人们对不同聚合物类型的毒性知之甚少。本研究旨在阐明小型微塑料（1-5 微米）对大西洋鲑鱼细胞的物理影响。来自肠道、血液的免疫细胞，和头肾暴露于绿色荧光聚乙烯微塑料 (PE-MP)、黄色荧光聚苯乙烯微塑料 (PS-MP) 和两者。分别对高 (50 mg/L)、中 (5 mg/L) 和低 (0.05 mg/L) 浓度进行了 1、24、48 和 72 小时的测试，以研究细胞死亡率和微塑料吸收。首次通过成像流式细胞术获得鱼类免疫细胞对微塑料摄取的定量数据。鲑鱼免疫细胞对微塑料的吞噬能力相对较低。在暴露于高浓度 48 小时后，不到 6% 的细胞摄入了颗粒。细胞也以低速率（<0.1%）吞噬低浓度的微塑料。与 PS-MPs 相比，PE-MPs 被更高百分比的细胞吞噬，前者及时生物积累，而后者随着时间的推移而减少。然而，每个细胞通常比 PE-MPs 吞噬更多的 PS-MPs 颗粒。来自不同组织的细胞对微塑料聚合物表现出不同的反应。总之，这项研究表明大西洋鲑鱼的免疫细胞可以吞噬微塑料，其影响取决于微塑料类型。PE-MPs 是海洋中最丰富的聚合物，也是鲑鱼养殖中广泛使用的塑料，比 PS-MPs 更容易被吸收。此外，该研究展示了成像流式细胞术如何应用​​于微塑料研究。海洋中最丰富的聚合物和鲑鱼养殖中广泛使用的塑料，比 PS-MP 更容易被吸收。此外，该研究展示了成像流式细胞术如何应用​​于微塑料研究。海洋中最丰富的聚合物和鲑鱼养殖中广泛使用的塑料，比 PS-MP 更容易被吸收。此外，该研究展示了成像流式细胞术如何应用​​于微塑料研究。