Endothelin and vascular remodelling in colitis pathogenesis-Appendicitis and appendectomy limit colitis by suppressing endothelin pathways

Appendicitis and appendectomy(AA), when done at a young age, offer protection against inflammatory bowel disease (IBD) development in later life. However, IBD pathogenesis involves both immunological and vascular abnormalities. Using the first murine model of AA (developed by us), we aimed to determine the role of AA in modulating vascular remodelling mediated by endothelin activity in IBD. Mice with two laparotomies each served as controls (sham-sham or SS). Distal colons were harvested (four AA group colons, four SS group colons), and RNA extracted from each. The RNA was subjected to microarray analysis and RT-PCR validation. Gene set enrichment analysis (GSEA) software was used to further analyze the microarray data. Gene expression of seven genes closely associated with endothelin activity was examined in distal colons 3 days post-AA and 28 days post-AA. While there were no gene expression changes 3 days post-AA, the genes EDN1 (0.7-fold), EDN2 (0.8-fold) and ECE2 (0.8-fold) were downregulated (*p value < 0.05) 28 days post-AA. However, EDN3 (1.3-fold) was upregulated 28 days post-AA (*p value < 0.05). GSEA analysis showed downregulation of 11 gene sets (stringent cut-offs-false discovery rate < 5 % and p value < 0.001) associated with endothelin and endothelin-converting enzyme genes by AA, in contrast to only 1 being upregulated. AA induces a delayed but significant suppression of genes pertaining to endothelin activity. Elucidating the pathways involved in suppression of endothelin activity and manipulation of different genes/enzymes/proteins related to endothelin activity will significantly enhance the extant repertoire of therapeutic options in IBD.