Pre-exposure to Fe 2 O 3 or TiO 2 Nanoparticles Inhibits Subsequent Biological Uptake of 55 Fe-Labeled Fe 2 O 3 Nanoparticles.

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 () to FeO or TiO NPs on the protozoan's subsequent uptake of Fe-labeled FeO (FeO) 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 FeO 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 FeO NPs. The differentially expressed metabolites obtained from the metabolomic experiments showed an enrichment of energy metabolism and antioxidation pathways in pre-exposed to NPs. Together, these results demonstrate that the pre-exposure of to FeO or TiO NPs inhibited the protozoan's subsequent uptake of FeO 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.