Blood
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Protease-activated receptors (PARs) activate Gq and G(12/13) pathways, as well as Akt (protein kinase B [PKB/Akt]) in platelets. However, the relative contribution of different G-protein pathways to Akt phosphorylation has not been elucidated. We investigated the contribution of Gq and G(12/13) to Gi/Gz-mediated Akt phosphorylation downstream of PAR activation. ⋯ Selective G(12/13) activation resulted in Src kinase activation, and Akt phosphorylation induced by costimulation of G(12/13) and Gi/Gz was inhibited by a Src kinase inhibitor but not by a Rho kinase inhibitor. These data demonstrate that G(12/13), but not Gq, is essential for thrombin-induced Akt phosphorylation in platelets, whereas Gq indirectly contributes to Akt phosphorylation through Gi stimulation by secreted ADP. G(12/13) activation might mediate its potentiating effect through Src activation, and Src kinases play an important role in thrombin-mediated Akt phosphorylation.
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Transfusion-related acute lung injury (TRALI) is a hazardous complication of transfusion and has become the leading cause of transfusion-related death in the United States and United Kingdom. Although leukoagglutinating antibodies have been frequently shown to be associated with the syndrome, the mechanism by which they induce TRALI is poorly understood. ⋯ Rather, antibody-mediated activation of neutrophils seems to initiate TRALI, a process that could be triggered by neutrophil stimulation with fMLP. Antibody-mediated neutrophil activation and subsequent release of reactive oxygen species may thus represent key events in the pathophysiologic cascade that leads to immune TRALI.