@article{KoesslerHermannWeberetal.2016,
  author    = {Koessler, Juergen and Hermann, Stephanie and Weber, Katja and Koessler, Angela and Kuhn, Sabine and Boeck, Markus and Kobsar, Anna},
  title     = {Role of Purinergic Receptor Expression and Function for Reduced Responsiveness to Adenosine Diphosphate in Washed Human Platelets},
  series = {PLoS One},
  volume    = {11},
  journal   = {PLoS One},
  number    = {1},
  doi       = {10.1371/journal.pone.0147370},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-146400},
  pages     = {e0147370},
  year      = {2016},
  abstract  = {Background Washing of platelets is an important procedure commonly used for experimental studies, e.g. in cardiovascular research. As a known phenomenon, responsiveness to adenosine diphosphate (ADP) is reduced in washed platelets, although underlying molecular mechanisms—potentially interfering with experimental results—have not been thoroughly studied. Objectives Since ADP mediates its effects via three purinergic receptors P2Y1, P2X1 and P2Y12, their surface expression and function were investigated in washed platelets and, for comparison, in platelet-rich-plasma (PRP) at different time points for up to 2 hours after preparation. Results In contrast to PRP, flow cytometric analysis of surface expression in washed platelets revealed an increase of all receptors during the first 60 minutes after preparation followed by a significant reduction, which points to an initial preactivation of platelets and consecutive degeneration. The activity of the P2X1 receptor (measured by selectively induced calcium flux) was substantially maintained in both PRP and washed platelets. P2Y12 function (determined by flow cytometry as platelet reactivity index) was partially reduced after platelet washing compared to PRP, but remained stable in course of ongoing storage. However, the function of the P2Y1 receptor (measured by selectively induced calcium flux) continuously declined after preparation of washed platelets. Conclusion In conclusion, decreasing ADP responsiveness in washed platelets is particularly caused by impaired activity of the P2Y1 receptor associated with disturbed calcium regulation, which has to be considered in the design of experimental studies addressing ADP mediated platelet function.},
  language  = {en}
}
@article{WolfBraunHainingetal.2016,
  author    = {Wolf, Karen and Braun, Attila and Haining, Elizabeth J. and Tseng, Yu-Lun and Kraft, Peter and Schuhmann, Michael K. and Gotru, Sanjeev K. and Chen, Wenchun and Hermanns, Heike M. and Stoll, Guido and Lesch, Klaus-Peter and Nieswandt, Bernhard},
  title     = {Partially Defective Store Operated Calcium Entry and Hem(ITAM) Signaling in Platelets of Serotonin Transporter Deficient Mice},
  series = {PLoS One},
  volume    = {11},
  journal   = {PLoS One},
  number    = {1},
  doi       = {10.1371/journal.pone.0147664},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-146399},
  pages     = {e0147664},
  year      = {2016},
  abstract  = {Background Serotonin (5-hydroxytryptamin, 5-HT) is an indolamine platelet agonist, biochemically derived from tryptophan. 5-HT is secreted from the enterochromaffin cells into the gastrointestinal tract and blood. Blood 5-HT has been proposed to regulate hemostasis by acting as a vasoconstrictor and by triggering platelet signaling through 5-HT receptor 2A (5HTR2A). Although platelets do not synthetize 5-HT, they take 5-HT up from the blood and store it in their dense granules which are secreted upon platelet activation. Objective To identify the molecular composite of the 5-HT uptake system in platelets and elucidate the role of platelet released 5-HT in thrombosis and ischemic stroke. Methods: 5-HT transporter knockout mice (5Htt\(^{-/-}\)) were analyzed in different in vitro and in vivo assays and in a model of ischemic stroke. Results In 5Htt\(^{-/-}\) platelets, 5-HT uptake from the blood was completely abolished and agonist-induced Ca2+ influx through store operated Ca\(^{2+}\) entry (SOCE), integrin activation, degranulation and aggregation responses to glycoprotein VI (GPVI) and C-type lectin-like receptor 2 (CLEC-2) were reduced. These observed in vitro defects in 5Htt\(^{-/-}\) platelets could be normalized by the addition of exogenous 5-HT. Moreover, reduced 5-HT levels in the plasma, an increased bleeding time and the formation of unstable thrombi were observed ex vivo under flow and in vivo in the abdominal aorta and carotid artery of 5Htt\(^{-/-}\) mice. Surprisingly, in the transient middle cerebral artery occlusion (tMCAO) model of ischemic stroke 5Htt\(^{-/-}\) mice showed nearly normal infarct volume and the neurological outcome was comparable to control mice. Conclusion Although secreted platelet 5-HT does not appear to play a crucial role in the development of reperfusion injury after stroke, it is essential to amplify the second phase of platelet activation through SOCE and plays an important role in thrombus stabilization.},
  language  = {en}
}