As wortmannin did not influence the PAR mediated Ca signalling, it is actually achievable the late stage of PAR induced PKC activation occurs by means of a PIK dependent mechanism rather than with the PLC DAG Ca pathway. Because PAR induced PLC signalling was fairly transient , the maintenance of GPIIb IIIa publicity and platelet aggregation may possibly largely depend on PIK mediated late PKC activation. Indeed, we observed that submit addition of TPA could attenuate the inhibition of PAR induced platelet aggregation developed by wortmannin. In contrast, each PAR AP induced PKC activation and Ca mobilization have been prolonged and relatively resistant for the results of wortmannin, indicating that PIK will not perform an essential role in PAR signalling, and this would also describe why PAR AP can induce irreversible platelet aggregation from the absence of PIK action.
From the situation NXY-059 of thrombinactivated platelets, disaggregation only occurred when platelets have been taken care of with each wortmannin and YD , suggesting that PIK mediated PKC activation and PAR mediated signalling, in particular the prolonged i elevation, are two independent and redundant pathways, activation of both pathway is enough to keep thrombin induced irreversible platelet aggregation. Akt is the significant downstream target of PIK. Activated PIK generates PI P phospholipids, which are critical for the recruitment of Akt into membranes, and Akt is consequently activated via phosphorylation at Thr by phosphoinositide dependent kinase . For complete activation, Akt calls for phosphorylation at Ser by a mammalian target of Rap . Genetic or pharmacological disruption of Akt is shown to impair platelet secretion and also to delay platelet aggregation, but there are no major defects from the stability of platelet aggregates .
Inside a quite latest research, an Akt inhibitor was showed to reverse PAR mediated platelet aggregation ; on the other hand, this will have to be interpreted with caution as we observed that in the concentrations reported, Akt inhibitor X induced platelet activation by itself as judged by platelet form change . In the current review, we used two structurally unique inhibitors of Akt, that may be, SH Bergenin and Akt inhibitor V, to more investigate the relationship among Akt and PIK dependent PKC activation. The two Akt inhibitors efficiently lowered phosphorylation on the Akt substrate GSKb without non precise results on platelet activation. Not like wortmannin, the Akt inhibitors failed to have an impact on PAR AP or thrombin induced PKC activation.
Steady with these information, Akt inhibitors alone or in combination using a PAR antagonist also failed to reverse platelet aggregation in response to PAR AP or thrombin. These effects indicate that in PAR or thrombin stimulated platelets, Akt is simply not the most important regulator of PIK dependent PKC activation and cannot account for PIK mediated irreversible platelet aggregation. A different prospective candidate for this purpose is PDK , which lies between PIK and Akt.