Decreased expression of occludin in the intestine of patients with inflammatory bowel disease

Permeability of the intestinal epithelium is regulated by both the transcellular and paracelluiar pathways. The main component of the paracellular pathway is the tight junction. Occludin, a 65kDa integral membrane protein, is the first transmembrane protein identified exclusively at the tight junction. Increases in intestinal permeability are well documented in several inflammatory conditions of the intestine including enteritis induced by non-steroidal anti-inflammatory drug use, celiac sprue, and idiopathic inflammatory bowel disease (IBD). The two major types of IBD are Crohn's Disease (CD) and Ulcerative Colitis (UC). To explore the molecular basis for this increased permeability we have studied the expression of occludin in intestinal mucosal specimens from patients with CD, UC, and normal controls. Our findings show that there is a marked decrease in the amount of occludin in the intestinal mucosa of both patients with CD and UC when compared with the normal patients. These findings suggest an alteration of the intestinal tight junction in this disease process that may relate to the increased intestinal permeability seen in IBD, especially CD.