Activated platelets in ulcerative colitis enhance the production of reactive oxygen species by polymorphonuclear leukocytes

Background: Although the number of activated platelets increases in the per ipheral blood of patients with inflammatory bowel disease (IBD), the role o f activated platelets in the polymorphonuclear leukocytes (PMN)-mediated mu cosal injury in IBD remains unclear. In the present study, we used luminol- enhanced chemiluminescence (LCL) to examine the influence of platelets from patients with ulcerative colitis (UC) on the production of reactive oxygen species EROS) by circulating PMN. Methods: The proportion of P-selectin-po sitive activated platelets was determined using flow cytometry. PMN from pa tients with UC and normal controls were stimulated using phorbol 12-myrista te 13-acetate with or without autologous platelets, anti-P-selectin monoclo nal antibody and thrombin. Indicator PMN from a normal volunteer were stimu lated using heterologous platelets from UC patients and normal controls, an d LCL signals were registered every 60 see for 240 min. Results: The propor tion of activated platelets was significantly increased in IBD patients. Th e level of ROS production by PMN did not significantly differ between UC pa tients and normal controls in the absence of a platelet-PMN interaction. Pl atelets from UC patients enhanced the amount of ROS produced by indicator P MN significantly more than those from normal controls. This effect was part ly diminished by anti-P-selectin monoclonal antibody. Conclusions: Platelet activation in UC might be responsible for the secondary activation of PMN, which could account for the increase in PMN-mediated tissue injury associa ted with UC.