ristocetin and Atherosclerosis

The plasma level of soluble CD40 ligand (sCD40L), which induces pro-inflammatory and pro-atherogenic responses, is known to be elevated in atherosclerotic patients. In this study, we investigated the mechanism of sCD40L release from human platelets, focusing on the involvement of thromboxane (TX) A(2).. We measured sCD40L release and TXA(2) production induced by ristocetin, an activator of GPIb/IX/V, from human platelets in vitro. Moreover, plasma sCD40L and TXA(2) levels in the 10 patients with severe carotid artery stenosis who were not taking any anti-platelet medicines were measured and compared with those obtained from non-atherosclerotic controls.. Ristocetin significantly promoted sCD40L release and TXA(2) generation from platelets in vitro. Aspirin and SC-560, a cyclooxygenase-1 inhibitor, suppressed the ristocetin-induced sCD40L release from platelets in parallel with TXA(2) production. Ozagrel, a TXA(2) synthase inhibitor and PTXA(2), a thromboxane receptor (TP) antagonist also suppressed sCD40L release. U46619, a TP agonist, reversed the suppressive effect of aspirin on sCD40L release. In vivo, plasma levels of sCD40L and TXA(2) in the patients were significantly higher than those in controls. Elevated plasma levels of TXA(2) and sCD40L in the patients were markedly diminished after 7 days of 100mg aspirin administration.. These results strongly suggest that GPIb/IX/V activation induces sCD40L release via TXA(2) from human platelets, and that sCD40L release via TXA(2) generation from platelets in atherosclerotic patients are up-regulated.

Topics: 15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; Aged; Aspirin; Atherosclerosis; Blood Platelets; Carotid Artery Diseases; CD40 Ligand; Female; Humans; Male; MAP Kinase Kinase 4; Methacrylates; Middle Aged; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; p38 Mitogen-Activated Protein Kinases; Phosphorylation; Pyrazoles; Ristocetin; Thromboxane A2

The aim of the study was to investigate the protein expression and function of a novel secreted protein in the vascular system, named SCUBE1 for signal peptide, CUB (Complement proteins C1r/C1s, Uegf, and Bmp1) and epidermal growth factor-like (EGF)-like domain containing protein 1.. Immunohistochemical analysis demonstrated that the SCUBE1 staining is mainly confined to the intravascular platelet-rich thrombus in vascular tissue samples. While quantitative real-time RT-PCR verified that the SCUBE1 mRNA is expressed in human platelets, numerous immunolocalization techniques revealed that the preformed SCUBE1 protein is stored in the alpha-granules and translocated to the surface upon platelet stimulation. A smaller SCUBE1 fragment, possibly formed by limited proteolysis after being released from the storage granules, was detected in thrombus lysate by Western blot analysis. Interestingly, deposition of SCUBE1 into the subendothelial matrix of the atherosclerotic plaques was evidenced by immunohistochemistry. In addition, studies of platelet adhesion and ristocetin-induced platelet agglutination showed that fragments containing the amino-terminal EGF-like repeats were able to support platelet adhesion and enhance the ristocetin-induced platelet agglutination, respectively.. These data suggest that platelet-derived SCUBE1 could function as a novel adhesive molecule and its matrix-bound and soluble fragments may play critical (patho)physiological roles in cardiovascular biology.

Topics: Animals; Antibodies, Monoclonal; Atherosclerosis; Blood Platelets; Blotting, Western; Calcium-Binding Proteins; Gene Expression; Humans; Membrane Proteins; Mice; Mice, Inbred BALB C; Platelet Activation; Platelet Adhesiveness; Platelet Aggregation; Reverse Transcriptase Polymerase Chain Reaction; Ristocetin; RNA, Messenger