Nanoplastic uptake through ROS-induced plasma membrane damage exacerbates renal fibrosis under hypoxia

Exposure to environmental nanoplastics and renal hypoxia are two commonly encountered detrimental factors for human health. However, their combined effects on the kidney and the underlying mechanisms remain poorly understood. This study aimed to determine (1) whether hypoxia influences the renal uptake of nanoplastics and exacerbates kidney injury and fibrosis, and (2) the underlying mechanisms involved, with particular emphasis on the roles of reactive oxygen species (ROS) and plasma membrane damage. C57BL/6 mice were exposed to hypoxic conditions and orally administered polystyrene nanoplastics (PS‑NPs, 2.5 mg/kg/d) for 28 days. In vitro experiments employed NRK‑52E tubular epithelial cells and NRK‑49 F fibroblasts, with treatments including the antioxidant N‑acetylcysteine. Fluorescence microscopy, transmission electron microscopy, calcein permeability assays, and LDH-release assays were employed to detect nanoplastic uptake and plasma membrane integrity. Target gene expression was manipulated using siRNA-mediated knockdown or plasmid-based overexpression. Hypoxia markedly increases renal accumulation of PS‑NPs, thereby aggravating renal injury and fibrosis, whereas PS‑NPs alone produces no detectable effect. PS‑NPs are primarily taken up through plasma membrane damage induced by ROS under hypoxic conditions. Blocking endocytosis does not affect the cellular uptake of PS-NPs. Through combined RNA‑sequencing and functional assays, we revealed that the Rab3a/Sytl2 axis suppresses PS‑NP uptake by mediating membrane repair and attenuates hypoxia/PS‑NPs-induced partial epithelial-mesenchymal transition in tubular epithelial cells. Hypoxia‑induced ROS promotes nanoplastic uptake by disrupting plasma membrane, thereby accelerating renal injury and fibrosis. The Rab3a/Sytl2 axis serves as a key protective mechanism by maintaining membrane integrity and limiting nanoplastic uptake. These findings link environmental nanoplastic exposure to exacerbated renal pathology under hypoxic conditions and reveal promising targets for renal protection. Hypoxia promotes renal accumulation of nanoplastics, exacerbating kidney injury and fibrosis. Hypoxia-induced ROS enhance nanoplastic uptake, aggravating partial epithelial- mesenchymal transition in renal tubular epithelial cells. Nanoplastic uptake is dependent on ROS-mediated plasma membrane damage. Rab3a/Sytl2 axis maintains plasma membrane integrity and suppresses nanoplastic uptake.