Effect of Lysosomotropic Polyamineoxidase Inhibitor MDL-72527 on Platelet Activation.

BACKGROUND/AIMS The polyamine oxidase inhibitor MDL-72527 (N1,N4-bis(2,3-butadienyl)-1,4-butanediamine) were expected to increase the abundance of spermine, a powerful inhibitor of platelet activation. Nothing is known, however, on the sensitivity of platelet function and survival to MDL-72527 exposure. The present study thus explored whether MDL-72527 modifies function and survival of platelets without and with platelet activation by collagen related peptide (CRP). METHODS Platelets isolated from wild-type mice were exposed for 30 minutes to MDL-72527 (100 µM) with or without subsequent activation with CRP (2-5 µg/ml). Flow cytometry was employed to estimate cytosolic Ca2+-activity ([Ca2+]i) from Fluo-3 fluorescence, platelet degranulation from P-selectin abundance, integrin activation from αIIbβ3 integrin abundance, generation of reactive oxygen species (ROS) from DCFDA fluorescence, phospholipid scrambling of the cell membrane from annexin-V-binding, platelet volume from forward scatter and aggregation utilizing staining with CD9-APC and CD9-PE. RESULTS In the absence of CRP, exposure of platelets to MDL-72527 did not significantly modify [Ca2+]i, P-selectin abundance, αIIbβ3 integrin abundance, ROS, annexin-V-binding, and forward scatter. The addition of 2-5 µg/ml CRP was followed by significant increase of [Ca2+]i, P-selectin abundance, αIIbβ3 integrin activation, ROS abundance, annexin-V-binding, and aggregation as well as a significant decrease of forward scatter, all effects significantly blunted or virtually abolished in the presence of MDL-72527. CONCLUSIONS MDL-72527 is a powerful inhibitor of platelet activation, apoptosis and aggregation.