Objectives: 1) To investigate which neutrophil-derived proteins in feces most accurately reflect disease activity in inflammatory bowel disease. 2) To examine the extracellular release of these proteins by activated neutrophils and their stability in feces by in vitro study.
Methods: We studied 41 patients (91 samples) with ulcerative colitis (UC), 34 patients (105 samples) with Crohn's disease (CD), and 25 control subjects. Fecal levels of lactoferrin (Lf), polymorphonuclear neutrophil elastase (PMN-E), myeloperoxidase (MPO), and lysozyme (Lys) were measured by ELISA. We also measured fecal hemoglobin (Hb) and alpha 1-antitrypsin (alpha 1-AT), useful markers of disease activity in UC and CD, respectively. For the in vitro study, blood samples were stimulated with phorbol myristate acetate or latex beads. For the assessment of stability, homogenized stool samples were stored at 4 degrees C, 25 degrees C, and 37 degrees C for various periods.
Results: 1) Fecal Lf, PMN-E, MPO, and Lys concentrations were significantly increased in the active phase of the disease compared to the inactive phase in both UC and CD. 2) Fecal Lf, PMN-E, MPO, and Lys concentrations correlated significantly with fecal Hb concentration in UC, whereas fecal Lf, PMN-E, and MPO concentrations correlated significantly with alpha 1-AT concentration in CD. In UC, fecal Lf, PMN-E, MPO, and Lys concentrations were high in 15, 9, 14, and 14 samples, respectively, of 25 samples with normal Hb concentration. In CD, fecal Lf, PMN-E, and MPO concentrations were high in 19, 10, and 16 samples, respectively, of 30 samples with normal alpha 1-AT concentration. 3) The extracellular release of Lf was the most efficient and this molecule was the most stable in feces.
Conclusions: Both our clinical and our in vitro studies suggested that Lf is the most suitable of these proteins to use as neutrophil-derived fecal marker of inflammation for clinical application.