Defensin modulates functional activity of platelets

Effect of human defensins on the cytoplasmic Ca2+ content in platelets

“…In our experiments, low concentrations of defensms (1-40 ~tg/ ml) inhibited the ago,list-induced [Ca2*]i rise in platelets. These findings agree with the data obtained in our previous experiments demonstrating that the same concentrations of defensins prevent platelet aggregation and platelet secretion of ATP induced by thrombin, collagen, or ADP [2,10]. These findings indicate that the inhibitory effect of defensins on platelet aggregating and secretory activities is realized via alterations in the free intracellular Ca 2 § Inhibition of the agonist-induced Ca 2+ in the platelet cytoplasm occurred irrespective of the type of inductor (thrombin, ADP, LPS of the S. typhimurium endotoxin).…”

“…The cationic proteins defensins (HNP), which are among the least investigated of these, have not only antimicrobial but also other biological properties [6,9]. Previously, we demonstrated that along with known substances released by activated polymorphonuclear leukocytes (cathepsin G, elastase, nitrogen oxide, and arachidonic acid metabolites) defensins can help regulate the functional activity of the platelets [2,10]. Human defensins induced by thrombin, collagen, or adenosin diphosphate (ADP) inhibit platelet aggregation and the secretion of adenosine triphosphate by platelets.…”