(61g) Proteomics-Informed Identification of Luminal Targets for in Situ Diagnosis of Inflammatory Bowel Disease

Introduction: Inflammatory bowel disease (IBD) includes several inflammatory conditions of the gastrointestinal tract (GIT), resulting in impaired intestinal homeostasis. The increasing incidence and prevalence of these conditions makes IBD an emerging global disease.¹ Current clinical practices for diagnosis and treatment of IBD are invasive, demanding and inefficient. Thus, we hypothesized that global proteomics analysis could serve as a helpful tool for identifying biomarkers for non-invasive IBD diagnosis. By finding IBD associated proteins, we can then modify flame-made superparamagnetic nanoparticles (SPION)^2,3 with suitable ligands to target the inflamed area of the GIT. This would allow the simultaneous detection and localization of inflammation by using magnetic resonance imaging (MRI).

Methods: The global intestinal proteomes from commonly used in vitro and in vivo models of IBD were analyzed. The in vitro model includes filter-grown Caco-2 cells exposed to either DSS (dextran sodium sulfate) or a mixture of cytokines and lipopolysaccharides. The in vivo model comprises mice (n=7) treated with 3% DSS in their drinking water for 7 days in order to induce acute colitis. Biopsies were collected from the small intestine as well as the distal and proximal segments of the colon. Based on data from global proteomics, selected protein biomarkers were stained to immunohistochemically evaluate protein location and accessibility from the luminal side of the GIT.

Results: Global proteomics analysis revealed upregulated plasma membrane proteins in intestinal segments of proximal- and distal colon from dextran sulfate sodium-treated mice and also in inflamed human intestinal Caco-2 cells pretreated with pro-inflammatory agents. The upregulated colon proteins in mice were compared to the proteome of the healthy ileum, to ensure targeting of diagnostic agents to the inflamed colon. Promising target proteins for future investigations of non-invasive diagnosis of IBD were found in both systems and included Tgm2/TGM2, Icam1/ICAM1, Ceacam1/CEACAM1, and Anxa1/ANXA1. Ultimately, these findings will guide the selection of appropriate antibodies for surface functionalization of imaging agents aimed to target inflammatory biomarkers in situ.

Conclusions: Global proteomics enables the identification and quantification of overexpressed proteins in experimental IBD models. Proteomics data revealed the presence of Tgm2/TGM2, Icam1/ICAM1, Ceacam1/CEACAM1, and Anxa1/ANXA1 in the plasma membrane of intestinal epithelial cells both in vitro and in vivo. These proteins are thereby promising, clinically relevant targets for development of diagnostic imaging probes that can easily be studied across the different experimental IBD models. Furthermore, these findings will support the development of non-invasive SPION-based biosensors for accurate detection of inflamed tissue in the GIT by MRI.

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