TY  - JOUR
A1  - Elgheznawy, Amro
A1  - Öftering, Patricia
A1  - Englert, Maximilian
A1  - Mott, Kristina
A1  - Kaiser, Friederike
A1  - Kusch, Charly
A1  - Gbureck, Uwe
A1  - Bösl, Michael R.
A1  - Schulze, Harald
A1  - Nieswandt, Bernhard
A1  - Vögtle, Timo
A1  - Hermanns, Heike M.
T1  - Loss of zinc transporters ZIP1 and ZIP3 augments platelet reactivity in response to thrombin and accelerates thrombus formation in vivo
JF  - Frontiers in Immunology
N2  - Zinc (Zn2+) is considered as important mediator of immune cell function, thrombosis and haemostasis. However, our understanding of the transport mechanisms that regulate Zn2+ homeostasis in platelets is limited. Zn2+ transporters, ZIPs and ZnTs, are widely expressed in eukaryotic cells. Using mice globally lacking ZIP1 and ZIP3 (ZIP1/3 DKO), our aim was to explore the potential role of these Zn2+ transporters in maintaining platelet Zn2+ homeostasis and in the regulation of platelet function. While ICP-MS measurements indicated unaltered overall Zn2+ concentrations in platelets of ZIP1/3 DKO mice, we observed a significantly increased content of FluoZin3-stainable free Zn2+, which, however, appears to be released less efficiently upon thrombin-stimulated platelet activation. On the functional level, ZIP1/3 DKO platelets exhibited a hyperactive response towards threshold concentrations of G protein-coupled receptor (GPCR) agonists, while immunoreceptor tyrosine-based activation motif (ITAM)-coupled receptor agonist signalling was unaffected. This resulted in enhanced platelet aggregation towards thrombin, bigger thrombus volume under flow ex vivo and faster in vivo thrombus formation in ZIP1/3 DKO mice. Molecularly, augmented GPCR responses were accompanied by enhanced Ca2+ and PKC, CamKII and ERK1/2 signalling. The current study thereby identifies ZIP1 and ZIP3 as important regulators for the maintenance of platelet Zn2+ homeostasis and function.
KW  - platelets
KW  - zinc
KW  - ZIP
KW  - thrombin
KW  - signaling
KW  - thrombosis
Y1  - 2023
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-320154
VL  - 14
ER  - 
TY  - JOUR
A1  - Wolf, Karen
A1  - Braun, Attila
A1  - Haining, Elizabeth J.
A1  - Tseng, Yu-Lun
A1  - Kraft, Peter
A1  - Schuhmann, Michael K.
A1  - Gotru, Sanjeev K.
A1  - Chen, Wenchun
A1  - Hermanns, Heike M.
A1  - Stoll, Guido
A1  - Lesch, Klaus-Peter
A1  - Nieswandt, Bernhard
T1  - Partially Defective Store Operated Calcium Entry and Hem(ITAM) Signaling in Platelets of Serotonin Transporter Deficient Mice
JF  - PLoS One
N2  - 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.
KW  - platelets
KW  - serotonin
KW  - integrins
KW  - blood flow
KW  - collagens
KW  - platelet activation
KW  - platelet aggregation
KW  - ischemic stroke
Y1  - 2016
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-146399
VL  - 11
IS  - 1
ER  -