Indomethacin-induced generation of reactive oxygen species leads to epithelial cell injury before the formation of intestinal lesions in mice.

Recently, with the increasing number of elderly patients who continuously take aspirin and/or nonsteroidal anti-inflammatory drugs (NSAIDs), the number of cases of severe hemorrhagic gastrointestinal (GI) bleeding is also on the increase. Gastric acid has been reported to play the most important role in hemorrhagic gastric mucosal injury. However, the pathogenesis of NSAID-derived mucosal injury in the intestine, where there is no acidic environment, remains unknown. We previously reported that NSAID-derived mitochondrial reactive oxygen species (ROS) are directly involved in GI cellular injury in vitro, although an in vivo study has not yet been carried out. In this study, we investigated the relationship between NSAID-derived ROS and intestinal injury formation. For this purpose, intestinal mucosal live imaging in mice was carried out using an ROS-indicating fluorescent probe. Treatment with indomethacin caused macroscopic intestinal injury in mice; however, many dying cells were observed even in areas that macroscopically appeared to have no injury after treatment with indomethacin. A fluorescent probe revealed that mucosal cells in the apparently uninjured areas had a high concentration of ROS. Treatment with rebamipide significantly decreased both the ROS concentration and the number of dying cells: this drug is prescribed clinically for gastric injury patients and has been reported to upregulate the expression of manganese superoxide dismutase. On the basis of these results, we propose that NSAID treatment causes a high cellular concentration of ROS in mucosae, possibly decreasing mucosal organo-protective efficacy. Moreover, intestinal food contents are likely to damage the mucosal structure when it is in such a fragile condition.