Malondialdehyde Drives a Feed-Forward Reactive Oxygen Species Loop in Pediatric Crohn’s Disease

PURPOSE: Crohn's disease (CD) is a chronic, relapsing inflammatory bowel disease with multifactorial etiology. Recent studies implicate reactive oxygen species (ROS) in pediatric CD. Expression of malondialdehyde (MDA), a biomarker of oxidative stress, is elevated in inflammatory diseases, including CD. This study aimed to evaluate genes driving ROS production in pediatric CD and MDA's role in shaping downstream gene expression.

METHODS: Using the Search Tag Analyze Resource for NCBI's Gene Expression Omnibus (STARGEO), we performed a tagged meta-analysis of publicly available gene expression data comparing pediatric CD with controls. Differentially expressed genes were restricted to p < 0.05 and absolute experimental log ratio of 0.2 for further analysis with Ingenuity Pathway Analysis (IPA), to explore biologic relationships.

RESULTS: Fifty-two pediatric CD samples and 24 healthy pediatric intestinal samples were identified and analyzed via STARGEO, yielding 1968 genes that met inclusion criteria. DUOX2, MMP3, and NOD2 were significantly upregulated in pediatric CD (log ratios of 2.521, 1.823, 0.524, respectively). Upstream regulators include TNF (z-score 11.195), TGFB1 (5.945), IFNG (9.983), and TLR4 (5.989). MDA was identified as a strongly activated regulator with a z-score of 10.909 and downstream targets including TGFB1, MMP3, TNF, and IL-6.

CONCLUSION: Our findings enhance the current understanding of the role of immune dysregulation, ROS, the gut microbiome, and epithelial barrier dysfunction in pediatric CD. DUOX2 functions as one of the central mediators of ROS-driven dysregulation, with TLR4-driven DUOX2 activity potentially overriding the NOD2 regulation. MDA formation stimulates inflammation and tissue injury, upregulating MMP3, which in turn increases ROS production to generate more MDA. This feed-forward inflammatory loop may accelerate fibrosis and chronic inflammation. This meta-analysis provides a preliminary framework of ROS-related gene programs in pediatric CD.