Effect of mesalazine on mucosal immune biomarkers in irritable bowel syndrome: a randomized controlled proof-of-concept study.

Intestinal immune infiltration contributes to symptoms in patients with irritable bowel syndrome (IBS). To assesses the effect of mesalazine (mesalamine) on mucosal immune cells in patients with IBS, through a pilot study. A randomized, double-blind, placebo-controlled trial in 20 patients with IBS in tertiary care setting. Patients were randomized to receive placebo or 800 mg mesalazine three times daily for 8 weeks. The primary endpoint was a significant reduction in total colonic immune cells on biopsies obtained at the end of treatment compared to baseline. Secondary endpoints included effects on subsets of immune cells, inflammatory mediators and symptom severity. Intention-to-treat analysis was performed. Mesalazine markedly reduced immune cells as compared with placebo (P = 0.0082); this effect was ascribed to a marked inhibition of mast cells (P = 0.0014). Mesalazine significantly increased general well-being (P = 0.038), but had no significant effects on abdominal pain (P = 0.084), bloating (P = 0.177) or bowel habits. No serious drug-related adverse events were reported during the study. Mesalazine is an effective and safe approach to reduce mast cell infiltration and may improve general well-being in patients with IBS. These results support the hypothesis that immune mechanisms represent potential therapeutic targets in IBS.