InductiOn Of SUperOXide aniOn prOductiOn frOm mOnOCyteS and neutrOphilS by activated plateletS thrOUgh the P-Selectin-sialyl

Abstract: Activated platelets expressing P-selectin on their surface are known to adhere to monocytes and neu-trophils. We examined the possibility that the leukocytes were activated by their adhesion to activated platelets and demonstrated that P-selectin-dependent platelet adhesion to neutrophils and monocytes induced produc-tion of extracellular superoxide anion (02-) by these leu-kocytes. Leukocyte membrane glycoproteins containing Ser/Thr-linked carbohydrate chains were responsiblc for the signal reception leading to the leukocyte activation. Cytokines were shown to influence these processes. For example, treatments of neutrophils with interleukin-8 (IL-8) or granulocyte colony-stimulating factor (G-CSF) potentiated the P-selectin-induced 02- production. Fur-thermore, interleukin-1 (IL-1) and interferon-1r (IFN-1r) induced surface expression of P-selectin on platelets in the presence of a low concentration of thrombin and con-sequently enhanced their adhesion capacity to leuko-cytes. These results indicated that the adhesion of acti-vated platelets to the leukocytes through the interaction between P-selectin and its carbohydrate ligand, sialyl Lewis X (Lex), was a crucial step for the activation of leukocyte function and supported the notion that acti-vated platelets were actively involved in the inflamma