Retinoic acid orchestrates NRF2 and FTH to alleviate iron-aggravated gut redox imbalance in E. coli-challenged piglets

Background The swine industry is vital to agriculture, and piglet health and growth are crucial to breeding efficiency. Bacterial infections are a particular concern and could lead to complications that further impact piglet health. Iron supplementation is essential for piglet health; however, excessive iron can lead to oxidative stress, potentially worsening these issues. This study explores the interplay between bacterial infection and cellular redox imbalances induced by high dietary iron and assesses the protective effects of retinoic acid (RA), providing insights for improving intestinal health and growth efficiency in piglets. To address these objectives, piglet models were developed for three key experiments. In the first experiment, piglets were infected with Escherichia coli ( E. coli ) to investigate the effect of bacterial infection on intestinal health and iron metabolism. In the second experiment, piglets were fed a high iron diet (1000 mg/kg FeSO ₄ ) for three weeks prior to infection with E. coli to determine how dietary iron impacts the effects of bacterial infection on intestinal health and iron metabolism. The third experiment utilized a 2 × 2 × 2 factorial design) to evaluate the effects of two dietary iron levels (100 and 1000 mg/kg FeSO ₄ ), two RA supplementation doses (0 and 5 mg every 2 days), and presence or absence of E. coli infection. Samples were analyzed to determine the effects on intestinal morphology, oxidative stress related markers. To compliment the tissue data, IPEC-J2 cells were used in experiments simulating high iron conditions with FeSO ₄ and bacterial virulence using lipopolysaccharide (LPS). Results These experiments revealed that E. coli infection disrupted intestinal structure, reduced the expression of SLC40A1 and FTL , and resulted in elevated ROS levels. A high iron diet exacerbated ROS and lipid peroxidation, while RA supplementation improved intestinal health by upregulating antioxidant defenses (NRF2 signaling) and reducing labile iron (FTH activation). These findings suggest that RA has promise as a potential therapeutic agent to mitigate iron overload and infection-induced intestinal damage, as well as offer insights into improving piglet intestinal health.