TFEB coordinates adaptive lysosome-to-secretory trafficking for exosome-enriched small extracellular vesicle-mediated reduction of intracellular polystyrene nanoplastic burden

Due to their resistance to intracellular degradation, environmental nanoplastics accumulate within hepatocytes, creating persistent particulate stress that challenges cellular homeostasis. While hepatic NP toxicity has been extensively investigated, the adaptive mechanisms by which hepatocytes reduce intracellular NP burden remain poorly understood. Here, we demonstrate that hepatocytes engage an adaptive lysosome-to-secretory trafficking program to limit the intracellular accumulation of polystyrene nanoplastics (PS-NPs). Following the removal of extracellular PS-NPs, intracellular PS-NP-associated signals progressively declined in parallel with increased recovery of PS-NP-associated fluorescence in exosome-enriched small extracellular vesicle (sEV) fractions. Airyscan super-resolution imaging further revealed a three-dimensional spatial association between a subset of intracellular PS-NP-associated signals and CD63-positive vesicular compartments. Intracellular PS-NP accumulation induced adaptive endolysosomal remodeling characterized by enhanced lysosomal acidification, increased extracellular recovery of lysosomal hydrolase activity, and activation of transcription factor EB (TFEB) through dephosphorylation and nuclear translocation. Functional analyses showed that TFEB activation or stimulation of TRPML-dependent lysosomal Ca²⁺ signaling enhanced intracellular PS-NP reduction, whereas inhibition of lysosomal function, blockade of exosome-enriched sEV secretion, TFEB depletion, or Rab27a silencing markedly impaired this adaptive response. Notably, Rab27a knockdown abolished the PS-NP-reducing effect of TFEB activation, supporting the conclusion that efficient intracellular PS-NP reduction depends on intact downstream vesicular secretion. Together, these findings support a hierarchical model in which TFEB coordinates adaptive lysosome-to-secretory trafficking, whereas Rab27a executes terminal vesicular secretion associated with extracellular recovery of PS-NP-associated material and reduction of intracellular PS-NP burden. This study defines an adaptive hepatocellular response to persistent intracellular particulate stress and provides a mechanistic framework for understanding cellular adaptation to non-biodegradable nanoplastics.