Inflammatory responses induced by synergistic actions between nanoplastics and typical heavy metal ions in human cells

Abstract

Nanoplastics (NPs) may transport heavy metal ions into organisms as vectors in an aquatic environment. The combination of NPs and heavy metal ions is deemed to pose health risks by ingestion into the human body through the food chain. In this study, 16 mixtures of ion-adsorbed polystyrene NPs (PS-ions) were prepared, and their ways of induction of inflammatory responses in human intestinal epithelial cell lines (Caco-2) and human monocytic leukemia cell (THP-1)-differentiated macrophages were investigated. The results indicated that PS-ions significantly increased the expression of inflammatory cytokines and intracellular ions exhibited a potential role in the inflammation caused by PS NPs. The machine learning models indicated that Cd²⁺ and Pb²⁺ were crucial for the increased expression of pro-inflammatory cytokines in THP-1 macrophages and Caco-2 cells, respectively. In addition, the activation of nuclear factor-κB (NF-κB) in THP-1 macrophages and extracellular signal-regulated kinase (ERK1/2) in the mitogen-activated protein kinase (MAPK) family in Caco-2 cells was identified to be associated with the high expression of pro-inflammatory cytokines. These results emphasize the synergistic effect between NPs and heavy metal ions and provide new insights into the combined health risks of NPs and heavy metal ions.