Colonic expression of leukotriene-pathway enzymes in inflammatory bowel diseases

Background: Leukotrienes derived from the 5-lipoxygenase pathway are proinflammatory lipid mediators that possibly play a role in inflammatory bowel diseases. The expression of 5-lipoxygenase pathway proteins has not previously been examined in colonic mucosa in inflammatory bowel disease. Results: Quantitative immunohistochemical analyses showed that, compared to those of the control subjects (n = 9), colonic biopsies from patients with active inflammatory bowel disease (n = 17) had 3- to 7-fold higher mean counts of cells expressing 5-lipoxygenase (P = 0.03), 5-lipoxygenase-activating protein (P = 0.005), and the leukotriene A(4) hydrolase (P 0.004). which make up the biosynthetic pathway of the potent neutrophil chemotaxin leukotriene B-4 immunoexpression of the leukotriene C-4 synthase was unaltered (P > 0.2). The increased representation of leukotriene B-4-pathway enzymes was associated with higher counts of neutrophils (P = 0.0001), macrophages (P = 0.03), eosinophils (P = 0.0004), CD8(+) T cells (P < 0.001), activated T cells (P < 0.05). and B cells (P < 0.05) but not of mast cells (P < 0.9). These eicosanoid and cellular changes were most marked in the subgroup of patients with ulcerative colitis (n = 9), and were absent in patients with quiescent disease (n = 6). The anomalies in the 5-lipoxygenase pathway were accompanied as expected by more cells immunostaining for cytokine-inducible COX-2 (P = 0.004, n = 17), but this Study also revealed a greater number of cells expressing COX-1 in the samples from the patients in the ulcerative colitis subgroup (P = 0.03, n = 9). Conclusions: The 5-lipoxygenase data provide a Cellular basis for increased tissue synthesis of the leukotriene B-4, as reflected in the colonic mucosa and rectal dialysates of patients with active inflammatory bowel disease, which contributes to neutrophil influx and colonic injury. The COX-1/COX-2 data hilghlight the ambiguous functional role of prostaroid pathways in inflammatory bowel diseases.