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[F. Others] F-3

Increased clearance of non-biodegradable polystyrene

nanoplastics by exocytosis through the inhibition of their

retrograde transport inside cells

Seung-Woo Han¹, Byung-Kwon Jung¹, Jin-Sil Bae¹, Ye-Jin Cho¹, Kwon-Yul Ryu¹*

¹Department of Life Science, University of Seoul, Seoul 02504, Korea

Nanoplastics (NPs) are derived from plastics, which may cause potential health risk. We have previously shown that
intracellular accumulation of PS (polystyrene)-NPs induced cyto- and neuro-toxicity through inflammatory and

oxidative stress. We also found that uptake of 100 nm-sized PS-NPs occurred via endocytosis, and they accumulated
at juxtanuclear position. We speculated that PS-NPs were cleared from the cells when they were no longer exposed

to PS-NPs. However, it remains unknown how PS-NPs behave inside cells and affect cellular machineries.
Accumulation of PS-NPs at juxtanuclear position could be due to retrograde transport along microtubules. To

investigate this possibility, we treated cells with the inhibitor of dynein, HDAC6, or microtubule polymerization, after
exposure to PS-NPs. We found that intracellular and juxtanuclear accumulation was greatly diminished under these

conditions. Interestingly, rapid clearance of PS-NPs was observed when cells were treated with the HDAC6 inhibitor.
PS-NPs were removed by exocytosis, which was confirmed by the exocytosis inhibitor treatment. Furthermore,
hampering retrograde transport of PS-NPs alleviated the activation of antioxidant response pathway. In sum, our

results suggest that the inhibition of retrograde transport of non-biodegradable PS-NPs leads to their rapid

clearance by exocytosis, which may reduce the cytotoxicity of PS-NPs.