@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}
}
@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{KobsarKoehnlechnerKlingleretal.2022,
  author    = {Kobsar, Anna and Koehnlechner, Karina and Klingler, Philipp and Niklaus, Marius and Zeller-Hahn, Julia and Koessler, Angela and Weber, Katja and Boeck, Markus and Koessler, Juergen},
  title     = {The effect of short-term refrigeration on platelet responsiveness},
  series = {Scientific Reports},
  volume    = {12},
  journal   = {Scientific Reports},
  number    = {1},
  doi       = {10.1038/s41598-022-21124-4},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-301390},
  year      = {2022},
  abstract  = {Storage of platelet concentrates (PC) at cold temperature (CT) is discussed as an alternative to the current standard of storage at room temperature (RT). Recently, we could show that cold-induced attenuation of inhibitory signaling is an important mechanism promoting platelet reactivity. For developing strategies in blood banking, it is required to elucidate the time-dependent onset of facilitated platelet activation. Thus, freshly prepared platelet-rich-plasma (PRP) was stored for 1 and 2 h at CT (2-6 °C) or at RT (20-24 °C), followed by subsequent comparative analysis. Compared to RT, basal and induced vasodilator-stimulated phosphoprotein (VASP) phosphorylation levels were decreased under CT within 1 h by approximately 20\%, determined by Western blot analysis and flow cytometry. Concomitantly, ADP- and collagen-induced threshold aggregation values were enhanced by up to 30-40\%. Furthermore, platelet-covered areas on collagen-coated slides and aggregate formation under flow conditions were increased after storage at CT, in addition to induced activation markers. In conclusion, a time period of 1-2 h for refrigeration is sufficient to induce an attenuation of inhibitory signaling, accompanied with an enhancement of platelet responsiveness. Short-term refrigeration may be considered as a rational approach to obtain PC with higher functional reactivity for the treatment of hemorrhage.},
  language  = {en}
}
@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{SchosseeVeitGitteletal.2022,
  author    = {Schossee, Nadine and Veit, Gabriele and Gittel, Julia and Viebahn, Johannes and Niklaus, Marius and Klingler, Philipp and {\"U}{\c{c}}eyler, Nurcan and Klinker, Erdwine and Kobsar, Anna and Boeck, Markus and Koessler, Juergen},
  title     = {Profile of the single-use, multiple-pass protein A adsorber column in immunoadsorption},
  series = {Vox Sanguinis},
  volume    = {117},
  journal   = {Vox Sanguinis},
  number    = {3},
  doi       = {10.1111/vox.13205},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-259689},
  pages     = {393-398},
  year      = {2022},
  abstract  = {Background and Objectives Immunoadsorptions (IA) are used to remove autoantibodies from the plasma in autoimmune disorders. In this study, we evaluated the effects of a single-use, recombinant staphylococcal protein A-based immunoadsorber on blood composition of the patient. Materials and Methods In a cohort of patients with myasthenia gravis or stiff-person syndrome, essential parameters of blood cell count, coagulation, clinical chemistry or plasma proteins and immunoglobulins (Ig) were measured before and after IA (n = 11). Results In average, IA reduced the levels of total IgG, IgG1, IgG2 and IgG4 by approximately 60\%, the acetylcholine receptor autoantibody levels by more than 70\%. IgG3, IgA or IgM were diminished to a lower extent. In contrast to fibrinogen or other coagulation factors, the column markedly removed vitamin K-dependent coagulation factors II, VII, IX and X by approximately 40\%-70\%. Accordingly, international normalized ratio and activated partial thromboplastin time were increased after IA by 59.1\% and 32.7\%, respectively. Coagulation tests almost returned to baseline values within 24 h. Blood cell count, electrolytes, total protein or albumin were not essentially affected. No clinical events occurred. Conclusion The single-use, multiple-pass protein A adsorber column is highly efficient to remove IgG1, IgG2 and IgG4 or specific acetylcholine receptor autoantibodies from the plasma. Coagulation parameters should be monitored, since the column has the capacity to largely reduce vitamin K-dependent factors.},
  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}
}