Peroxiredoxin 1 expression in active ulcerative colitis mucosa identified by proteome analysis and involvement of thioredoxin based on immunohistochemistry

Ulcerative colitis (UC) is a chronic, relapsing, inflammatory bowel disease, and patients with long-standing UC are at high risk of developing colorectal cancer as a typical case of the organ-specific chronic inflammation-carcinoma sequence. Interactions between epithelial and stromal cells and alterations in a variety of stromal microenvironments have been demonstrated to have important roles in the carcinogenesis of UC-associated carcinoma. Therefore, the identification of proteins in the inflammatory microenvironment is important not only in the epithelium, however also in the stroma of UC inflammatory foci. To identify proteins associated with UC-associated carcinoma, the present study used proteomic analysis with two-dimensional electrophoresis and mass spectrometry. Differentially expressed proteins were assessed between active and inactive UC biopsy specimens. Results were verified by immunohistochemistry. Peroxiredoxin 1 (PRDX1) was among the proteins identified to have increased expression in active compared with inactive UC. Immunohistochemical analysis indicated that the expression of both PRDX1 and thioredoxin (TRX) increased with increasing inflammation grade in epithelial cells in UC mucosal crypts. PRDX1-positive stromal cells in the lower half of the lamina propria increased along with colitis severity. Furthermore, the expression of both PRDX1 and TRX proteins was increased in UC-associated neoplastic lesions compared with normal mucosa. A stepwise increase in PRDX1 expression was clear with increasing tumor progression in UC-associated tumorigenesis. Since PRDX1 and TRX overexpression was a unique characteristic of UC activity and UC-associated neoplastic lesions, PRDX1 and TRX expression may reflect oxidative stress along with the severity of colitis activity and UC-associated tumorigenesis in patients with UC.