Abstract

Background With the escalating issue of polystyrene microplastic pollution, microplastic particles have been detected in human urine. While calcium oxalate (CaOx) crystals are well-established mediators of renal stone formation, the role of microplastics, particularly polystyrene nanoplastics (PS-NPs), in promoting CaOx kidney stone formation remains unclear. This study aims to explore whether PS-NPs interact with CaOx crystals to enhance renal tubular epithelial cell injury and facilitate the formation of kidney stones. Methods Clinical CaOx kidney stone samples were analyzed using pyrolysis—gas chromatography-mass spectrometry (Py-GC/MS), which detected microplastic components. In vitro, human renal proximal tubular epithelial cells (HK-2) were exposed to calcium oxalate monohydrate crystals (1.5 mM), or cells were pretreated with PS-NPs (100 nm, 0.1 mg/mL) for 24 h, followed by the addition of 1.5 mM CaOx for co-treatment. Comprehensive mechanistic assessments, including whole-transcriptome RNA sequencing, crystal adhesion assays, macrophage chemotaxis and polarization analysis, ferroptosis biomarker quantification, lipid peroxidation measurement, and mitochondrial ferrous ion accumulation, were conducted. In vivo, a rat model of CaOx nephrolithiasis was induced by ethylene glycol (EG) with concurrent exposure to PS-NPs (4 mg/Kg·Day) via drinking water. Results Clinical analysis confirmed the presence of PS-NPs and other microplastics in human CaOx kidney stones. In vitro, exposure to PS-NPs significantly altered the morphology of CaOx crystals, promoting aggregation and enhancing adhesion to renal tubular epithelial cells. Combined exposure to PS-NPs and CaOx crystals exacerbated HK-2 cell injury through upregulation of VCAM1, CXCL8-driven macrophage chemotaxis and M1 polarization, and ferroptosis induced by xCT/GPX4 suppression. Transcriptomic analysis revealed LRP6 downregulation as a central regulator in these pathological processes. Overexpression of low-de