Matrix metalloproteinase inhibitors attenuate endotoxemia induced cardiac dysfunction: A potential role for MMP-9

Enhanced cardiac generation of peroxynitrite contributes to septic cardiomyopathy. Since matrix metalloproteinases ( MMPs) are activated in vitro by peroxynitrite, we hypothezised that MMPs may contribute to cardiac mechanical dysfunction in sepsis. Rats were injected (i.p.) with either lipopolysaccharide (LPS, 4 mg/kg) or vehicle. MMP inhibitors, either Ro 31-9790 (20 mg/kg), doxycycline (4 mg/kg), or vehicle were administered i.p. 30 min after LPS. At 6 h, when the symptoms of endotoxemia peak, hearts were excised and perfused as working hearts with Krebs-Henseleit buffer at 37degreesC. Cardiac work (cardiac output x peak systolic pressure product) was measured. Perfusate and ventricle samples were analyzed by gelatin zymography to quantify MMP activity. Cardiac function was significantly depressed in LPS-treated rats compared to control rats (control: 55 +/- 4, LPS: 26 +/- 6 mmHg*mL*min(-1)). LPS also caused a loss of 72 kDa MMP-2 activity in the ventricles and the perfusate. Although MMP-9 activity was not detected in the ventricles, LPS resulted in an increase in perfusate 92 kDa MMP-9 activity. The MMP inhibitors significantly improved cardiac function of LPS-treated rats (Ro 31-9790: 38 +/- 3, doxycycline: 51 +/- 3 mmHg*mL*min(-1)), had no effect on the loss of MMP-2 activity, and significantly reduced the MMP-9 activity in the perfusate. These results demonstrate, for the first time, that LPS induced cardiac dysfunction is associated with a loss in ventricular MMP-2 activity and the release of MMP-9 from the heart. MMP inhibitors can significantly preserve cardiac mechanical function during septic shock.