Evaluation of biotransformation of sulphasalazine in the colon epithelial Caco-2 cells.

Sulphasalazine (salicyl-azo-sulphapiridine, SAS) is a drug commonly used in the treatment of non-specific inflammatory bowel diseases, such as ulcerative colitis and Crohn disease. Chronic inflammatory states of the colon can lead to neoplastic changes of the intestinal mucosa. There are some suggestions in the literature that the intestinal bacterial azo-reductases are involved in biotransformation of SAS into 5-aminosalicylic acid (5-ASA) and sulphapyridine (SP). For this reason, it seemed worth of investigating whether transformation of SAS could be performed by the colon epithelial cells themselves. No enzymatic systems presumably exist in Caco-2, which could be responsible for SAS metabolism, because after 72 h-incubation of cell cultures with 1 mM SAS, its metabolites i.e., 5-ASA and SP were not detected in cells, neither in culture media. SAS metabolism, therefore, seems to depend on the presence of intestinal bacterial enzymatic systems. It was confirmed that 5-ASA is converted by Caco-2 cells to N-acetyl-5-aminosalicylic acid (Ac-5-ASA), which migrates to the culture medium. The other metabolite of SAS i.e., SP, was not transformed in the human colon cancer cells at all.