Moderate inhibition of myocardial matrix metalloproteinase-2 by ilomastat is cardioprotective

Pharmacological inhibition of matrix metalloproteinase-2 (MMP-2) is a promising target for acute cardioprotection against ischemia/reperfusion injury. Therefore, here we investigated if the MMP inhibitor ilomastat administered either before ischemia or before reperfusion is able to reduce infarct size via inhibition of MMP-2, the most abundant MMP in the rat heart.Infarct-size limiting effect of ilomastat (0.3–6.0 μmol/kg) was tested in an in vivo rat model of myocardial infarction induced by 30 min coronary occlusion/120 min reperfusion. Ilomastat at 0.75 and 1.5 μmol/kg decreased infarct size significantly as compared to the vehicle-treated (dimethyl sulfoxide) group (from 66.1 ± 4.6% to 45.3 ± 7.0% and 46.7 ± 5.5% of area at risk, p < 0.0.5, respectively), when administered 5 min before the onset of ischemia. Ilomastat at 6.0 μmol/kg significantly reduced infarct size from its control value of 65.4 ± 2.5% to 52.8 ± 3.7% of area at risk (p < 0.05), when administered 5 min before the onset of reperfusion. Area at risk was not significantly affected by ilomastat treatments. To further assess the cytoprotective effect of ilomastat, primary cardiomyocytes isolated from neonatal rats were subjected to 240 min simulated ischemia followed by 120 min simulated reperfusion in the presence of ilomastat (5 nM–5 μM). Ilomastat at 500 nM and 5 μM significantly increased cell viability when compared to vehicle treated group. To assess the in situ MMP-2 inhibitory effect of ilomastat, in separate experiments in situ zymography was performed in cardiomyocytes. The cytoprotective concentration of ilomastat (500 nM) showed a moderate (approximately 25%) inhibition of intracellular MMP-2 in ischemic/reperfused cardiomyocytes. In these cells, MMP-2 immunostaining showed a 90% colocalization with the in situ gelatinolytic activity.We conclude that the MMP inhibitor ilomastat reduces infarct size when administered either before the onset of ischemia or before the onset of reperfusion in vivo. Furthermore, this is the first demonstration that a moderate inhibition of intracellular MMP-2 is sufficient to confer cardiocytoprotection.

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