Diabetes Type 2: Circulating Phosphatidylserine-Expressing Platelets Regulate Whole Blood Agonist-Evoked Platelet Activity In Vitro
Abstract Background Platelet agonists responses in vitro (i.e., reactivity) include the creation of phosphatidylserine (PS)-exposing platelets together with the activation of the fibrinogen receptors (α IIb β 3 ) and lysosomal exocytosis. It is feasible to judge the activation pathways by analyzing platelet surface annexin V, the activated fibrinogen receptor (PAC-1), and the release of lysosomal-associated membrane protein (LAMP-1), correspondingly. We postulate that, in type 2 diabetes (T2DM), surface PS of circulating platelets, unprovoked in vitro , links with whole blood (WB) agonist-induced responses. Patients and Methods After informed consent, T2DM subjects ( n = 35) were enrolled. A Percoll gradient (1.09–1.04 kg/L) separated their normal-sized platelets according to density into subpopulations ( n = 8). A flow cytometer analyzed surface annexin V (mean fluorescence intensity [MFI]) of the subfractions, unprovoked ex vivo. The datasets were subsequently correlated with platelet WB agonist-induced responses (i.e., annexin V, PAC-1, and LAMP-1 [all MFI]) to α-thrombin (10 μM), cross-linked collagen-related peptide (CRP-XL, 0.15 μg/mL), and adenosine diphosphate (ADP, 5 μM) in vitro. Results Surface annexin V (MFI) of most platelet subfractions and the magnitudes of WB agonist-induced annexin V (MFI) of normal-sized platelets in vitro associated closely. Such PS-expressing platelets also linked inversely with WB agonist-evoked surface PAC-1 (MFI) (all used agonists) and LAMP-1 (MFI) (CRP-XL, ADP only). It is concluded that surface PS, unprovoked in vitro, of most density-separated platelets connected with platelet reactivity, i.e., their WB agonist-evoked reactions in the test tube.