Cathepsins K, L, B, X and W are differentially expressed in normal and chronically inflamed gastric mucosa.

The expression of cathepsins K, L, B, X and W was studied by quantitative RT-PCR in normal and inflamed gastric mucosa (antrum, corpus, cardia). Cathepsins B, L, K and X were expressed ubiquitously. In contrast, cathepsin W was expressed at very low levels. Infection by Helicobacter pylori caused a significant induction of cathepsin X (p<0.008), whereas the other cathepsins were not or only locally affected by H. pylori infection or reflux disease. Immunohistochemistry revealed specific expression of cathepsin X (macrophages), cathepsin K (parietal cells) and cathepsin W (lymphocytes), whereas cathepsins B and L were predominantly expressed in epithelial cells.