Ferroptosis and Wnt/β-Catenin Signaling Triggered by Environmentally Relevant Nanoscale Polypropylene Plastics in Human Intestinal Models

Nanoplastics generated through environmental weathering may disrupt epithelial barrier integrity by promoting oxidative damage and inflammation, yet most studies rely solely on pristine synthetic particles that lack surface chemistries representative of real-world aged plastics. Here, we investigated the biological effects of environmentally relevant nanoscale polypropylene reference material (NPPP-1) produced by laser ablation and evaluated its material-specific responses under matched particle-number exposure conditions, in comparison with pristine and ultraviolet-aged synthetic polypropylene in human small intestinal organoids (HSIOs) and human intestinal epithelial cells. NPPP-1 induced oxidative stress, with elevated reactive oxygen species (ROS), lipid peroxidation, and DNA oxidation, accompanied by upregulation of genes and proteins associated with inflammation, ROS, and cell death pathways. Functional assays revealed concomitant activation of ferroptosis, apoptosis, and pyroptosis. Ferroptosis was the primary driver of cell death, as evidenced by partial rescue of viability mediated by ferroptosis inhibitor ferrostatin-1. In HSIOs, NPPP-1 triggered nuclear translocation and accumulation of β-catenin and upregulated the Wnt target gene Axin2. Ferroptosis inhibition reduced Wnt upregulation, suggesting activation of regenerative signaling that serves to mitigate ferroptotic stress. Indeed, inhibition of this pathway increased lipid peroxidation and reduced viability, further indicating a compensatory response to counter ferroptotic stress. Imaging and spectroscopic analyses confirmed internalization of NPPP-1 within the epithelial layers, linking the presence of particles to biological effects. These findings demonstrate that environmentally relevant nanoscale plastics such as NPPP-1 elicit oxidative stress-driven cell death while simultaneously activating the Wnt/β-catenin pathway as a protective response. The combined degenerative and compensatory dynamics highlight the importance of using realistic nanoscale plastic materials and advanced 3D organoid systems to assess human health risks under conditions that mimic real-world exposures.