inositol-1-4-5-trisphosphate and Infarction--Middle-Cerebral-Artery

Activation of platelets by subendothelial collagen results in an increase of cytosolic Ca(2+) concentration ([Ca(2+)]i) and is followed by platelet activation and thrombus formation that may lead to vascular occlusion. The present study determined the role of phosphoinositide-dependent protein kinase 1 (PDK1) in collagen-dependent platelet Ca(2+) signaling and ischemic stroke in vivo.. Platelet activation with collagen receptor glycoprotein VI agonists collagen-related peptide or convulxin resulted in a significant increase in PDK1 activity independent of second-wave signaling. PDK1 deficiency was associated with reduced platelet phospholipase Cγ2-dependent inositol-1,4,5-trisphosphate production and intracellular [Ca(2+)]i in response to stimulation with collagen-related peptide or convulxin. The defective increase of [Ca(2+)]i resulted in a substantial defect in activation-dependent platelet secretion and aggregation on collagen-related peptide stimulation. Furthermore, Rac1 activation and spreading, adhesion to collagen, and thrombus formation under high arterial shear rates were significantly diminished in PDK1-deficient platelets. Mice with PDK1-deficient platelets were protected against arterial thrombotic occlusion after FeCl3-induced mesenteric arterioles injury and ischemic stroke in vivo. These mice had significantly reduced brain infarct volumes, with a significantly increased survival of 7 days after transient middle cerebral artery occlusion without increase of intracerebral hemorrhage. Tail bleeding time was prolonged in pdk1(-/-) mice, reflecting an important role of PDK1 in primary hemostasis.. PDK1 is required for Ca(2+)-dependent platelet activation on stimulation of collagen receptor glycoprotein VI, arterial thrombotic occlusion, and ischemic stroke in vivo.

Topics: 3-Phosphoinositide-Dependent Protein Kinases; Animals; Blood Platelets; Calcium Signaling; Collagen; Disease Models, Animal; Genetic Predisposition to Disease; Infarction, Middle Cerebral Artery; Inositol 1,4,5-Trisphosphate; Mice, Knockout; Neuropeptides; Phenotype; Phospholipase C gamma; Platelet Activation; Platelet Adhesiveness; Platelet Aggregation; Platelet Membrane Glycoproteins; rac1 GTP-Binding Protein; Thrombosis; Time Factors