Vitamin C Enema Advances Induction of Remission in the Dextran Sodium Sulfate-Induced Colitis Model in Rats

The current main treatment for ulcerative colitis (UC) is induction therapy by long-term administration of 5-aminosalicylic acid (5-ASA), but various side effects have been reported. Therefore, a radical cure for UC is desired. A vitamin C (VC) has anti-inflammatory effects. Therefore, this study investigated whether a VC solution enema shortens induction of remission in colitis model rats. Wistar rats (6 wk old/male) were allowed to freely ingest a 1% dextran sulfate sodium (DSS) solution for 10 d and then switched to tap water for normal breeding for 10 d (UC group). At the time of switching to tap water, an enema was performed with a 5-ASA solution (40 mg/kg/d) or VC solution (460 mg/kg/d) for 10 d. The neutrophil number, COX-2, which is an index of inflammation, and type III collagen, which is an early healing marker, were significantly increased in the UC group. However, the VC group showed decreases compared with UC groups. Furthermore, compared with UC and 5-ASA groups, the VC group showed increased expression of type I collagen, which is expressed late in healing, and significant epithelial regeneration was observed in colon tissue. The VC solution enema shortened the induction of remission by directly suppressing inflammation of damaged large intestinal tissues and promoting mucosal healing.