Aquatic organisms are frequently exposed to various nanoparticles (NPs) in the natural environment. Thus, studies of NP bioaccumulation should include organisms that have been previously exposed to NPs. Our study investigated the effects of pre-exposure of Tetrahymena thermophila (T. thermophila) to Fe₂O₃ or TiO₂ NPs on the protozoan’s subsequent uptake of ⁵⁵Fe-labeled Fe₂O₃ (⁵⁵Fe₂O₃) NPs. Molecular mechanisms underlying the pre-exposure effects were explored in transcriptomic and metabolomic experiments. Pre-exposure to either NPs inhibited the subsequent uptake of ⁵⁵Fe₂O₃ NPs. The results of the transcriptomic experiment indicated that NP pre-exposure influenced the expression of genes related to phagosomes and lysosomes and physiological processes such as glutathione and lipid metabolism, which are closely associated with the endocytosis of ⁵⁵Fe₂O₃ NPs. The differentially expressed metabolites obtained from the metabolomic experiments showed an enrichment of energy metabolism and antioxidation pathways in T. thermophila pre-exposed to NPs. Together, these results demonstrate that the pre-exposure of T. thermophila to Fe₂O₃ or TiO₂ NPs inhibited the protozoan’s subsequent uptake of ⁵⁵Fe₂O₃ NPs, possibly by mechanisms involving the alteration of endocytosis-related organelles, the induction of oxidative stress, and a lowering of the intracellular energy supply. Thus, NP pre-exposure represents a scenario which can inform increasingly realistic estimates of NP bioaccumulation.

中文翻译：

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预暴露于 Fe2O3 或 TiO2 纳米粒子会抑制随后生物摄取 55Fe 标记的 Fe2O3 纳米粒子

水生生物经常暴露于自然环境中的各种纳米粒子 (NPs)。因此，NP 生物蓄积研究应包括以前接触过 NP 的生物体。我们的研究调查了嗜热四膜虫( T. thermophila )预先暴露于 Fe ₂ O ₃或 TiO ₂ NPs 对原生动物随后摄取⁵⁵ Fe 标记的 Fe ₂ O ₃ ( ⁵⁵ Fe ₂ O ₃) 纳米粒子。在转录组学和代谢组学实验中探索了预暴露效应的分子机制。^{预先暴露于任一种 NP 都会抑制随后的55} Fe ₂ O ₃ NP摄取。转录组学实验结果表明，NP预暴露影响吞噬体和溶酶体相关基因的表达以及谷胱甘肽和脂质代谢等生理过程，这些与 55 Fe 2 O 3 NPs的^内吞_作用密切_相关。从代谢组学实验中获得的差异表达代谢物表明嗜热链球菌的能量代谢和抗氧化途径丰富预先接触 NPs。总之，这些结果表明T. thermophila预先暴露于 Fe ₂ O ₃或 TiO ₂ NPs 抑制了原生动物随后摄取⁵⁵ Fe ₂ O ₃ NPs，这可能是通过涉及内吞作用相关细胞器改变的机制，诱导氧化应激和细胞内能量供应的降低。因此，NP 预暴露代表了一种情景，可以为 NP 生物蓄积的越来越现实的估计提供信息。