The tire antioxidant derivative 6PPD-quinone exacerbates IBD by targeting NR1H4-mediated lipid metabolism and mitochondrial dysfunction in human colon epithelial cells.

Abstract

N- (1,3-Dimethylbutyl)-N'-phenyl-p-phenylenediamine quinone (6PPD-Q), a tire rubber antioxidant derivative, accumulates in air, soil, and water and has been found in urine, blood, and cerebrospinal fluid, posing significant health risks. Although 6PPD-Q exhibits intestinal toxicity, its role in inflammatory bowel disease (IBD) remains unclear. The objective of this study was to identify key molecular targets of 6PPD-Q in IBD and to validate their involvement in 6PPD-Q-induced intestinal epithelial cell injury. Using network toxicology, machine learning, molecular docking, and in vitro experiments in human intestinal epithelial cells, we identified 60 overlapping 6PPD-Q-IBD targets, enriched in lipid metabolism, oxidative stress, and inflammation. Multi-model machine learning screened six core genes (NR1H4, ANXA5, SPARC, PCK1, PDK2, and CFB), with NR1H4 as a key mediator. Molecular docking showed strong binding of 6PPD-Q to NR1H4, exceeding that of its parent compound. In vitro experiments confirmed that 6PPD-Q caused lipid droplet and cholesterol accumulation, mitochondrial dysfunction (manifested as ATP synthesis inhibition, mitochondrial ROS burst, decreased membrane potential, and mitochondrial fragmentation), and significantly upregulated the levels of pro-inflammatory cytokines IL-6, TNF-α, and IL-8, thereby triggering inflammatory responses. Moreover, 6PPD-Q exposure significantly downregulated NR1H4 expression. These findings reveal that 6PPD-Q increases IBD risk by interfering with lipid metabolism, disrupting mitochondrial function, upregulating inflammatory cytokines, and downregulating NR1H4, providing important evidence for understanding the risk posed by this emerging environmental pollutant to IBD and for developing preventive strategies.