Soy protein diet suppresses COX‐2 induction by dextran sodium sulfate in CD‐1 mouse colon.

Inflammatory bowel disease (IBD) affects nearly 1 million people per year and is associated with increased risk of colon cancer. Dextran sodium sulfate (DSS) is commonly used to induce mucosal tissue damage and an immune response in rodent colon that mimics IBD in humans. Cyclooxygenase‐2 (COX‐2) is typically associated with an inflammatory response and is an early marker of colon carcinogenesis. Activation of the wnt signaling pathway including release of β‐catenin, is associated with colon carcinogenesis. Dietary components, including soy proteins, may provide protection from inflammation induction. To define the role of dietary soy protein on DSS‐induced mucosal damage, female, CD‐1 mice were fed diets containing either 20% casein or soy protein. DSS (2%) was added to drinking water of half of the mice on each diet while the others received untreated water. Mice were euthanized 7 days later. Colon mucosa was collected into lysis buffer and frozen in liquid nitrogen. Extracts were processed for Western immunoblot using COX‐2 and β‐catenin antibodies. No change in body weight due to diet or DSS was observed. For mice fed the casein diet COX‐2 expression was increased 2.5 fold by DSS, whereas this effect was abrogated in mice fed soy protein. No differences in β‐catenin were observed. These results suggest soy protein may provide protection from inflammatory processes in colon leading to improvement in IBD.