Increased expression of matrix metalloproteinase (MMP)-2, -3 and -9 has been demonstrated in Crohn's disease fistulas, but it is unknown whether these enzymes are biologically active and represent a therapeutic target. Therefore, we investigated the proteolytic activity of MMPs in fistula tissue and examined the effect of inhibitors, including clinically available drugs that beside their main action also suppress MMPs. Fistula specimens were obtained by surgical excision from 22 patients with Crohn's disease and from 10 patients with fistulas resulting from other causes. Colonic endoscopic biopsies from six controls were also included. Total functional MMP activity was measured by a high-pressure liquid chromatography (HPLC)-based, fluorogenic MMP-substrate cleavage assay, and the specific activity of MMP-2, -3 and -9 by the MMP Biotrak Activity Assay. The MMP inhibitors comprised ethylene-diamine-tetraacetic acid (EDTA), the synthetic broad-spectrum inhibitor, GM6001, the angiotensin-converting enzyme (ACE) inhibitor, ramiprilate, and the tetracycline, doxycycline. In Crohn's disease fistulas, about 50% of the total protease activity was attributable to MMP activity. The average total MMP activity was significantly higher (about 3.5-times) in Crohn's fistulas (471 FU/µg protein, range 49-2661) compared with non-Crohn's fistulas [134 FU/µg protein, range 0-495, (p <0.05)] and normal colon [153 FU/µg protein, range 77-243, (p <0.01)]. MMP-3 activity was increased in Crohn's fistulas (1.4 ng/ml, range 0-9.83) compared with non-Crohn's fistulas, [0.32 ng/ml, range 0-2.66, (p <0.02)]. The same applied to MMP-9 activity [0.64 ng/ml, range 0-5.66 and 0.17 ng/ml, range 0-1.1, respectively (p <0.04)]. Ramiprilate significantly decreased the average total MMP activity level by 42% and suppressed the specific MMP-3 activity by 72%, which is comparable to the effect of GM6001 (87%). Moreover, MMP-9 activity was completely blunted by ramiprilate. Doxycycline had no effect on MMP activity. Increased functional MMP activity, notably MMP-3 and -9, is present in Crohn's fistulas and may be inhibited by ramiprilate, a widely available ACE inhibitor.
Basic and Clinical Pharmacology and Toxicology, 2011, Vol 109, Issue 3, p. 208-16