title: Glycoprotein IIb/IIIa inhibition attenuates platelet-activating factor-induced platelet activation by reducing protein kinase C activity.
abstract: Glycoprotein (GP)IIb/IIIa inhibition may abolish activated leukocyte-induced platelet activation, in which leukocyte-released platelet-activating factor (PAF) is a major mediator. The present study thus investigated if and how GPIIb/IIIa inhibitors interfere with PAF-induced platelet activation. Platelet and leukocyte activation were monitored by flow cytometry and immunoblotting. GPIIb/IIIa inhibitors (c7E3, non-peptide SR121566, and MAb RFGP56) attenuated PAF-induced, but not adenosine diphosphate (ADP)- or thrombin receptor activating peptide (TRAP)-induced platelet P-selectin expression in whole blood. GPIIb/IIIa blockade enhanced ADP- or TRAP-induced leukocyte CD11b expression, but not the response to PAF. GPIIb/IIIa blockade attenuated PAF-induced, but enhanced ADP- or TRAP-induced platelet-leukocyte aggregation. Under the present experimental conditions, thromboxane A2 receptor antagonism did not significantly influence PAF-induced platelet activation, and GPIIb/IIIa inhibition did not interfere with calcium mobilization/influx in platelets. Protein kinase C (PKC) blockade inhibited PAF-induced platelet P-selectin expression, and PAF-induced PKC activity was reduced by GPIIb/IIIa inhibition. PAF (=1 micro m) did not induce MEK 1/2 or ERK 1/2 phosphorylation, whilst thrombin induced marked responses, which were enhanced by GPIIb/IIIa blockade. Thus, GPIIb/IIIa inhibition attenuates PAF-induced platelet activation via inhibiting PKC activity. GPIIb/IIIa blockade enhances thrombin-induced platelet MEK 1/2 and ERK 1/2 activation, and augments ADP- and TRAP-induced leukocyte activation by enhancing platelet-leukocyte aggregation.
authors.affiliation: Department of Medicine, Karolinska Hospital, Karolinska Institute, Stockholm, Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Hu
authors.forename: W
authors.initials: W
authors.lastname: Zhang
authors.forename: N
authors.initials: N
authors.lastname: Li
mesh_terms: D000244:Adenosine Diphosphate / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D000911:Antibodies, Monoclonal; D001792:Blood Platelets / Q000378:metabolism; D039481:CD11b Antigen / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D015151:Immunoblotting; D007962:Leukocytes / Q000378:metabolism; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; D008297:Male; D008875:Middle Aged; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D019007:P-Selectin / Q000378:metabolism; D010446:Peptide Fragments / Q000378:metabolism; D010455:Peptides / Q000737:chemistry; D010766:Phosphorylation; D010972:Platelet Activating Factor / Q000378:metabolism*; D015539:Platelet Activation; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000037:antagonists & inhibitors*; D011493:Protein Kinase C / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000037:antagonists & inhibitors; D013997:Time Factors
chemical_list: D000911:Antibodies, Monoclonal; D039481:CD11b Antigen; D019007:P-Selectin; D010446:Peptide Fragments; D010455:Peptides; D010972:Platelet Activating Factor; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D044244:Receptors, Thromboxane A2, Prostaglandin H2; C086309:thrombin receptor peptide SFLLRNP; D000244:Adenosine Diphosphate; C482128:MAP2K2 protein, human; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D048369:MAP Kinase Kinase 1; D048370:MAP Kinase Kinase 2; C482125:MAP2K1 protein, human; D020929:Mitogen-Activated Protein Kinase Kinases