Matrix metalloproteinases are possible mediators for the development of alimentary tract mucositis in the dark agouti rat

Alimentary tract (AT) mucositis is a serious and debilitating side-effect of cancer therapy primarily characterized by damage of the mucous membranes throughout the AT. It is well established that this damage is a result of up-regulation of stress response genes and pro-inflammatory cytokines. Matrix metalloproteinases (MMPs) have been shown to function in several of the pathways known to be up-regulated in mucositis and play a key role in tissue injury and inflammation in many gastrointestinal disorders. This study aims to characterize the expression of multiple MMPs including MMP-1, -2, -3, -9 and -12 and their inhibitors, tissue inhibitor of metalloproteinase (TIMP)-1 and -2, in a rat model of irinotecan-induced mucositis. Dark agouti rats were administered a single 200 mg/kg intraperitoneal dose of irinotecan and killed at 1, 6, 24, 48, 72, 96 and 144 h following treatment. Hematoxylin and eosin staining, immunohistochemistry and realtime polymerase chain reaction were used to assess histopathological damage and MMP expression in the jejunum and colon. Marked histopathological evidence of mucositis was observed in the jejunum and colon as early as six hours following irinotecan treatment. A significant alteration in both gene expression and tissue levels of MMPs and TIMPs was noted following irinotecan. The increase in MMP-2, -3, -9 and -12 levels was associated with inflammatory infiltrate and maximum tissue damage. In contrast, MMP-1 expression correlated with tissue restitution. TIMP-1 and -2 levels were significantly altered in the jejunum following irinotecan. The augmentation in the expression profiles of MMPs and their inhibitors correlated with histopathological alterations observed in the tissue following irinotecan. This prompts the consideration of MMPs as possible mediators of chemotherapy-induced mucositis.