Abstract 3610: Direct Thrombin Inhibition Limits Ischemia and Reperfusion Injury in Rats by Decreasing Oxidative Stress, Apoptosis, and Inflammation
Background Myocardial ischemia and reperfusion injury involves the generation of oxygen free radicals and elicits apoptosis along with an inflammatory response. The objective of this study was to determine whether direct thrombin inhibition prevents ischemia and reperfusion injury by decreasing myocardial oxidative stress, apoptosis, and inflammation.
Methods/Results We evaluated the protective role of lepirudin in an in vivo rat model of ischemia and reperfusion. Lepirudin (5 mg/kg i.p.) or vehicle (control) was administered 15 min prior to LCA occlusion (30 min) and tissue analysis was performed after 120 min reperfusion. Control infarct size was 59±1% area at risk and Lepirudin reduced this infarct size to 25±2% area at risk. We assess oxidative stress by measuring the oxidative formation of [3Fe4S]+ using electron paramagnetic resonance spectroscopy. The oxidation of [3Fe4S]+ increased throughout reperfusion in control hearts and this increase was normalized by lepirudin. Nitric oxide (NO) inhibits xanthine oxidase activity. Xanthine oxidase is a major contributor to the post-ischemic production of free radicals. Therefore, we measured NOx levels and xanthine oxidase activity from the ischemic zone of the myocardium. Lepirudin augmented the increase in NOx levels (lepirudin 18±0.8 vs. control 12±0.5; sham 9±0.5 mmole/g tissue) and reduced xanthine oxidase activity (lepirudin 34 ±4 vs. control 137±13; sham 38±2 mU/g protein). No difference in xanthine oxidase activity or NOx levels was observed in non-ischemic tissue. Caspase-3 activity, a maker of apoptosis and myeloperoxidase activity, a marker of inflammation was also measured in the ischemic zone. Lepirudin reduced caspase-3 activity (lepirudin 120±10 vs. control 174±16; sham 91±8 U/mg protein) and myeloperoxidase activity (lepirudin 9±2 vs. control 21±3; sham 3±1mU/mg protein). (n=6/group, data is mean±SEM, p<0.05).
Conclusion Lepirudin-mediated protection against ischemia and reperfusion injury was associated with decreased oxidative stress by increasing NO production and decreasing xanthine oxidase activity and thereby limiting apoptosis and inflammation.