Selectin on activated platelets enhances neutrophil endothelial adherence in myocardial reperfusion injury

OBJECTIVES: The glycoprotein P-selectin is an adhesion molecule that is rapidly expressed on the surface of platelets and endothelium during the inflammatory process. P-selectin on endothelium has been reported to play an important role in reperfusion injury. However, little is known regarding P-selectin on platelets in contributing to the pathophysiology of myocardial reperfusion injury. In this study, we hypothesized that P-selectin on platelets may enhance neutrophil endothelial adherence and this may play a role in neutrophil-mediated reperfusion injury. METHODS: Endothelial cells, cardiomyocytes, platelets and neutrophils were isolated from adult rats. Endothelial cells and cardiomyocytes were cultivated in a co-culture system. After exposure to hypoxia and reoxygenation, neutrophil adherence and migration were examined. RESULTS: After exposure to 6 h of hypoxia, endothelial cells co-incubated with platelets showed significantly greater neutrophil adherence (63.1 +/- 4.0%) and migration (78.2 +/- 6.7%) than endothelial cells alone (adhesion: 44.2 +/- 2.8%, migration: 57.9 +/- 4.9%). These increases were significantly inhibited (adhesion: 42.1 +/- 3.5%, migration: 65.5 +/- 3.8%) by an anti-P-selectin monoclonal antibody. Moreover, the superoxide-anion production was significantly elevated when activated platelets were added to neutrophils. This enhanced production was also inhibited by anti-P-selectin antibody. CONCLUSION: The presence of activated platelets enhanced neutrophil adhesion and migration process after hypoxia reoxygenation. This process may occur following platelet-neutrophil interactions via P-selectin and subsequent neutrophil activation.