Aniline exposure induces intestinal inflammation and IBD-like pathological changes via ATF2-mediated apoptosis in mouse intestinal epithelial cells

Aniline is a widely distributed environmental pollutant, but its impact on gut health and underlying mechanisms remain poorly understood. This study investigated the effects of aniline on intestinal epithelial cell apoptosis and intestinal inflammation, and explored the role of the ATF2 signaling pathway using in vitro and in vivo models. IEC-6 rat intestinal crypt epithelial cells were treated with different concentrations of aniline (0, 2.5, 5, 10, 20, 40 mM). Cell viability, apoptosis, reactive oxygen species (ROS) production, and signaling pathway activation were assessed by CCK-8 assay, flow cytometry, and Western blotting. In vivo, eight-week-old male C57BL/6 mice without pre-existing intestinal disease were exposed to aniline by daily oral gavage (10, 20, 40 mg/kg) for 14 days. Ileal tissues were analyzed by histopathology, immunohistochemistry, and Western blotting. Aniline exposure significantly reduced IEC-6 cell viability (≥ 5 mM), induced apoptosis and ROS generation, and activated the p38 MAPK pathway, accompanied by upregulation of pro-apoptotic proteins Bax and Cleaved-caspase-3 and downregulation of tight junction proteins ZO-1, occludin, and claudin-1. In mice, aniline exposure led to shortened small intestine length, inhibition of weight gain, crypt architectural damage, and inflammatory cell infiltration, together with increased expression of TNF-α, IL-17, and CD68 and decreased tight junction proteins. These changes indicate intestinal inflammation and disruption of the intestinal barrier with morphological and molecular features that resemble experimental inflammatory bowel disease (IBD). Mechanistically, aniline exposure markedly activated the ATF2 signaling pathway in ileal tissues. Silencing ATF2 in IEC-6 cells significantly attenuated aniline-induced apoptosis, ROS production, and the expression of inflammation-related proteins. Collectively, our findings demonstrate that aniline promotes intestinal epithelial cell apoptosis and disrupts the mucosal barrier via activation of the ATF2 pathway, thereby inducing intestinal inflammation with IBD-like pathological features. This work provides mechanistic insight into how environmental pollutants such as aniline may contribute to intestinal inflammatory diseases and identifies ATF2 as a potential molecular target for mitigating pollutant-related gut injury. However, because classic clinical indicators of IBD (e.g., diarrhea, hematochezia, disease activity index) were not assessed, our model should be interpreted as chemically induced intestinal inflammation rather than a complete IBD model.