@article{KoesslerKlinglerNiklausetal.2020, author = {Koessler, Juergen and Klingler, Philipp and Niklaus, Marius and Weber, Katja and Koessler, Angela and Boeck, Markus and Kobsar, Anna}, title = {The Impact of Cold Storage on Adenosine Diphosphate-Mediated Platelet Responsiveness}, series = {TH Open}, volume = {4}, journal = {TH Open}, number = {3}, doi = {10.1055/s-0040-1714254}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-229387}, pages = {e163-e172}, year = {2020}, abstract = {Introduction  Cold storage of platelets is considered to contribute to lower risk of bacterial growth and to more efficient hemostatic capacity. For the optimization of storage strategies, it is required to further elucidate the influence of refrigeration on platelet integrity. This study focused on adenosine diphosphate (ADP)-related platelet responsiveness. Materials and Methods  Platelets were prepared from apheresis-derived platelet concentrates or from peripheral whole blood, stored either at room temperature or at 4°C. ADP-induced aggregation was tested with light transmission. Activation markers, purinergic receptor expression, and P2Y12 receptor function were determined by flow cytometry. P2Y1 and P2X1 function was assessed by fluorescence assays, cyclic nucleotide concentrations by immunoassays, and vasodilator-stimulated phosphoprotein (VASP)-phosphorylation levels by Western blot analysis. Results  In contrast to room temperature, ADP-induced aggregation was maintained under cold storage for 6 days, associated with elevated activation markers like fibrinogen binding or CD62P expression. Purinergic receptor expression was not essentially different, whereas P2Y1 function deteriorated rapidly at cold storage, but not P2Y12 activity. Inhibitory pathways of cold-stored platelets were characterized by reduced responses to nitric oxide and prostaglandin E1. Refrigeration of citrated whole blood also led to the attenuation of induced inhibition of platelet aggregation, detectable within 24 hours. Conclusion  ADP responsiveness is preserved under cold storage for 6 days due to stable P2Y12 activity and concomitant disintegration of inhibitory pathways enabling a higher reactivity of stored platelets. The ideal storage time at cold temperature for the highest hemostatic effect of platelets should be evaluated in further studies.}, language = {en} } @article{NiklausKlinglerWeberetal.2022, author = {Niklaus, Marius and Klingler, Philipp and Weber, Katja and Koessler, Angela and Kuhn, Sabine and Boeck, Markus and Kobsar, Anna and Koessler, Juergen}, title = {Platelet Toll-Like-Receptor-2 and -4 Mediate Different Immune-Related Responses to Bacterial Ligands}, series = {TH Open}, volume = {6}, journal = {TH Open}, number = {3}, doi = {10.1055/a-1827-7365}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-301401}, pages = {e156 -- e167}, year = {2022}, abstract = {Background  Like immune cells, platelets express toll-like receptors (TLRs) on their surface membrane. TLR2 and TLR4 are able to recognize bacterial antigens and have the potential to influence hemostatic functions and classical intracellular signaling pathways. This study investigated the role of TLR2 and TLR4 for immune-related functions in human platelets. Materials and Methods  Washed platelets and neutrophils were prepared from fresh human peripheral blood. Basal-, Pam3CSK4- (as TLR2 agonist) and Lipopolysaccharides (LPS; as TLR4 agonist) -induced CD62P expression, fibrinogen binding and TLR2 or TLR4 expression, intracellular reactive oxygen species (ROS) production in H2DCFDA-loaded platelets and uptake of fluorescence-labeled TLR ligands, and fluorophore-conjugated fibrinogen were evaluated by flow cytometry. Analysis of platelet-neutrophil complexes was performed after coincubation of washed platelets and neutrophils in the presence and absence of TLR2 or TLR4 agonists on poly-L-lysine coated surfaces, followed by immunostaining and immunofluorescence imaging. Results  Pam3CSK4 rapidly and transiently increased TLR2 and TLR4 expression. Over the course of 30 minutes after activation with Pam3CSK4 and LPS, the expression of both receptors decreased. Pam3CSK4-stimulated intracellular ROS production and the uptake of TLR ligands or fibrinogen much stronger than LPS. Besides, TLR4 activation led to a significant increase of platelet-neutrophil contacts. Conclusion  Stimulation leads to rapid mobilization of TLR2 or TLR4 to the platelet surface, presumably followed by receptor internalization along with bound TLR ligands. After activation, platelet TLR2 and TLR4 mediate different immune-related reactions. In particular, TLR2 induces intracellular responses in platelets, whereas TLR4 initiates interactions with other immune cells such as neutrophils.}, language = {en} } @phdthesis{Schuepferling2023, author = {Sch{\"u}pferling, Anne Marie Heidi}, title = {Der Einfluss der Proteasomhemmung durch Bortezomib auf die Aktivierbarkeit humaner Thrombozyten}, doi = {10.25972/OPUS-32755}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-327551}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {Bortezomib, ein selektiver und potenter Proteasominhibitor, wird experimentell in der Tumorzellforschung sowie therapeutisch in der Therapie des Multiplen Myeloms eingesetzt. Die Wirkung auf die Thrombozytenfunktion war bislang unzureichend untersucht. Daher evaluiert diese Studie die dosisabh{\"a}ngige Wirkung von Bortezomib auf die Viabilit{\"a}t, die Aggregation von gewaschenen Thrombozyten und auf aktivierende Signalwege in gewaschenen Thrombozyten. Die Thrombozytenviabilit{\"a}t war bei hohen Bortezomibkonzentrationen von 100 - 200 µM vermindert. Passend dazu verminderten 100 - 200 µM Bortezomib die Phosphorylierung der ERK1/2 und der Akt/PKB in humanen Thrombozyten. Im Gegensatz dazu hatten diese hohen Bortezomibkonzentrationen keinen Einfluss auf das Niveau der p38 MAP Kinase-Phosphorylierung in aktivierten Thrombozyten. Die Thrombozytenaggregation, induziert durch hohe Konzentrationen von Kollagen oder TRAP-6, blieb unter 0,1 nM - 200 µM Bortezomib unver{\"a}ndert. Zusammenfassend l{\"a}sst sich sagen, dass Bortezomib weder die essenziellen, aktivierenden Signalwege noch die Initialisierung der Aggregation relevant beeinflusst. Das zeigt, dass diese Prozesse in Thrombozyten nicht abh{\"a}ngig von der Proteasomaktivit{\"a}t sind. Supramaximale Inhibierung des Proteasomsystems mit Bortezomibkonzentrationen von 100 µM oder mehr f{\"u}hren m{\"o}glicherweise zu ver{\"a}nderter Thrombozytenreaktionsf{\"a}higkeit, welche unter Umst{\"a}nden durch unspezifische und potenziell toxische Effekte mit erniedrigter Zellviabilit{\"a}t verursacht werden.}, subject = {Thrombozyt}, language = {de} } @phdthesis{Klingler2023, author = {Klingler, Philipp}, title = {Exploration of proteasome interactions with human platelet function}, doi = {10.25972/OPUS-32108}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-321089}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {Platelets are anucleated cell fragments derived from megakaryocytes. They play a fundamental role in hemostasis, but there is rising evidence that they are also involved in immunological processes. Despite absence of a nucleus, human platelets are capable of de novo protein synthesis and contain a fully functional proteasome system, which is, in nucleated cells, involved in processes like cell cycle progression or apoptosis by its ability of protein degradation. The physiological significance of the proteasome system in human platelets is not yet fully understood and subject of ongoing research. Therefore, this study was conducted with the intention to outline the role of the proteasome system for functional characteristics of human platelets. For experimentation, citrated whole blood from healthy donors was obtained and preincubated with proteasome inhibitors. In addition to the commonly used bortezomib, the potent and selective proteasome inhibitor carfilzomib was selected as a second inhibitor to rule out agent-specific effects and to confirm that observed changes are related to proteasome inhibition. Irreversibly induced platelet activation and aggregation were not affected by proteasome blockade with bortezomib up to 24 hours. Conversely, proteasome inhibition led to enhanced threshold aggregation and agglutination up to 25 \%, accompanied by partial alleviation of induced VASP phosphorylation of approximately 10-15 \%. Expression of different receptors were almost unaffected. Instead, a significant increase of PP2A activity was observable in platelets after proteasome blockade, accompanied by facilitated platelet adhesion to coated surfaces in static experiments or flow chamber experiments. Carfilzomib, used for the first time in functional experimentation with human platelets in vitro, led to a dose-dependent decrease of proteasome activity with accumulation of poly ubiquitylated proteins. Like bortezomib, carfilzomib treatment resulted in enhanced threshold aggregation with attenuated VASP phosphorylation. As the main conclusion of this thesis, proteasome inhibition enhances the responsiveness of human platelets, provided by an alleviation of platelet inhibitory pathways and by an additional increase of PP2A activity, resulting in facilitated platelet adhesion under static and flow conditions. The proteasome system appears to be involved in the promotion of inhibitory counterregulation in platelets. The potential of proteasome inhibitors for triggering thromboembolic adverse events in patients must be clarified in further studies, in addition to their possible use for targeting platelet function to improve the hemostatic reactivity of platelets.}, subject = {Thrombozyt}, language = {en} } @article{KoesslerSchwarzWeberetal.2017, author = {Koessler, Juergen and Schwarz, Michaela and Weber, Katja and Etzel, Julia and Koessler, Angela and Boeck, Markus and Kobsar, Anna}, title = {The role of adenosine diphosphate mediated platelet responsiveness for the stability of platelet integrity in citrated whole blood under ex vivo conditions}, series = {PLoS ONE}, volume = {12}, journal = {PLoS ONE}, number = {11}, doi = {10.1371/journal.pone.0188193}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-159879}, pages = {e0188193}, year = {2017}, abstract = {Background: Platelets are important for effective hemostasis and considered to be involved in pathophysiological processes, e.g. in cardiovascular diseases. Platelets provided for research or for therapeutic use are frequently separated from citrated whole blood (WB) stored for different periods of time. Although functionally intact platelets are required, the stability of platelet integrity, e.g. adenosine diphosphate (ADP) mediated responsiveness, has never been thoroughly investigated in citrated WB under ex vivo conditions. Objectives: Platelet integrity was evaluated at different time points in citrated WB units, collected from healthy donors and stored for 5 days at ambient temperature. The analysis included the measurement of activation markers, of induced light transmission aggregometry and of purinergic receptor expression or function. Inhibitory pathways were explored by determination of basal vasodilator-stimulated phosphoprotein (VASP)-phosphorylation, intracellular cyclic nucleotide levels and the content of phosphodiesterase 5A. Fresh peripheral blood (PB) samples served as controls. Results: On day 5 of storage, thrombin receptor activating peptide-6 (TRAP-6) stimulated CD62P expression and fibrinogen binding were comparable to PB samples. ADP induced aggregation continuously decreased during storage. Purinergic receptor expression remained unchanged, whereas the P2Y1 activity progressively declined in contrast to preserved P2Y12 and P2X1 function. Inhibitory pathways were unaffected except for a slight elevation of VASP phosphorylation at Ser\(^{239}\) on day 5. Conclusion: After 5 days of storage in citrated WB, platelet responsiveness to TRAP-6 is sufficiently maintained. However, ADP-mediated platelet integrity is more sensitive to deterioration, especially after storage for more than 2 days. Decreasing ADP-induced aggregation is particularly caused by the impairment of the purinergic receptor P2Y1 activity. These characteristics should be considered in the use of platelets from stored citrated WB for experimental or therapeutic issues.}, language = {en} } @phdthesis{Wiebecke2023, author = {Wiebecke, Sophie Karolina}, title = {Einfluss mikrobieller Substanzen von Parodontitis-assoziierten Bakterien auf die Funktion humaner Thrombozyten}, doi = {10.25972/OPUS-32903}, url = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-329038}, school = {Universit{\"a}t W{\"u}rzburg}, year = {2023}, abstract = {Diese Arbeit untersuchte die Wirkung von bakteriellen Substanzen auf essenzielle thrombozyt{\"a}re Funktionen. Bei den Substanzen handelte es sich um Toxine von Bakterien, die mutmaßlich zur Pathogenese der Parodontitis beitragen. W{\"a}hrend LTX von Bakterium A. actinomycetemcomitans und C14 von F. nucleatum zur Hemmung der Aggregation und zur Stimulation inhibitorischer Systeme beitr{\"a}gt, induziert LPS von P. gingivalis eine leichte Aktivierung der Thrombozyten, gekennzeichnet durch eine gering verst{\"a}rkte P-Selektin-Expression.}, subject = {Parodontitis}, language = {de} }