Myeloperoxidase Enzyme Activity in Feces Reflects Endoscopic Severity in Inflammatory Bowel Disease

Concentrations of the neutrophil protein myeloperoxidase are elevated in the feces of individuals with endoscopically active inflammatory bowel disease (IBD). Its enzyme activity could give an immediate readout of endoscopic inflammation. We investigated whether fecal myeloperoxidase activity (fMPOa) is associated with IBD endoscopic inflammation. We also investigated whether myeloperoxidase promotes oxidative stress in IBD.

Myeloperoxidase enzyme activity was measured using an enzyme-linked immunosorbent assay (ELISA fMPOa), a novel CM-sepharose extraction assay (CM-S fMPOa), or by quantifying urinary glutathione sulfonamide (GSA) by tandem mass spectrometry. GSA is a specific biomarker of myeloperoxidase activity. IBD activity was assessed using the ulcerative colitis endoscopic index of severity or the simple endoscopic score for Crohn's disease (SES-CD). Spearman's correlation and receiver operating characteristic curves evaluated biomarker utility.

IBD patients (n = 172) were recruited prospectively (ulcerative colitis, n = 72; Crohn's disease, n = 100). fMPO was mostly active. Its enzyme activity, measured either as ELISA fMPOa or CM-S fMPOa, correlated with endoscopic inflammation in both ulcerative colitis and Crohn's disease. Urinary GSA is also correlated with endoscopic disease inflammation. Correlations of urinary GSA with disease measures and other biomarkers were stronger in ulcerative colitis than in Crohn's disease.

Myeloperoxidase is active in IBD and its enzyme activity is a reliable marker of IBD endoscopic inflammation. Our results with the CM-S fMPOa assay demonstrate the potential for an immediate and accurate measure of fMPO enzyme activity as a robust, low-cost test for IBD activity. Myeloperoxidase may contribute to tissue damage in IBD.