Synergism Between Platelets and Neutrophils in Provoking Cardiac Dysfunction After Ischemia and Reperfusion

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Abstract
Background —Neutrophils (PMNs) are known to contribute to both cardiac dysfunction and myocardial necrosis after reperfusion of an ischemic heart. Moreover, platelets are also important blood cells that can aggravate myocardial ischemic injury. This study was designed to test the effects of PMNs and platelets separately and together in provoking cardiac dysfunction in isolated perfused rat hearts after ischemia and reperfusion. Methods and Results —Control rat hearts not subjected to ischemia were perfused without blood cells for 80 minutes. Additional control rat hearts were perfused with 75×10 6 PMNs, with 100×10 6 platelets, or with 75×10 6 PMNs+100×10 6 platelets over a 5-minute perfusion followed by a 75-minute observation period. No significant reduction in coronary flow, left ventricular developed pressure (LVDP), or the first derivative of LVDP (dP/dt max ) was observed at the end of the observation period in any nonischemic group. Similarly, global ischemia (I) for 20 minutes followed by 45 minutes of reperfusion (R) produced no sustained effects on the final recovery of any of these parameters in any group of hearts perfused in the absence of blood cells. However, I/R hearts perfused with either PMNs or platelets alone exhibited decreases in these variables of 10% to 12% ( P P X -oligosaccharide or a recombinant soluble P-selectin ligand, which inhibits selectin-mediated cell adhesion. Conclusions —These results provide evidence that platelets and neutrophils act synergistically in provoking postreperfusion cardiac dysfunction and that this may be largely due to cell-to-cell interactions mediated by P-selectin. These findings may help explain the reperfusion injury phenomenon.