title: Evaluation of dose-dependent effects of the proteasome inhibitor bortezomib in human platelets.
abstract: Platelets express key proteins of the proteasome system and contain protein ubiquitination pathways. The functional role of the proteasome system in platelets, however, is still subject of studies. In addition to its role as anticancer drug, the potent and selective proteasome inhibitor bortezomib can be used for experimental proteasome research. Since it is mandatory to know exact dose-effect relationships, we intended to evaluate dose-dependent specific bortezomib effects on basal and on agonist-induced proteasome activitiy, on levels of poly-ubiquitinated proteins and on platelet aggregation. In washed platelets, unstimulated or stimulated with different agonists and pre-incubated with various bortezomib concentrations, the proteasome activity was determined by a fluorometric assay. The levels of poly-ubiquitinated proteins were assessed by an immunoassay kit. Platelet aggregation was measured by light transmission aggregometry in platelet-rich-plasma. Platelet agonists stimulate both, the proteasome activity and the accumulation of poly-ubiquitinated proteins in platelets. Bortezomib inhibits the basal and the agonist induced proteasome activity and increased the content of poly-ubiquitinated proteins in a concentration dependent manner. Bortezomib concentrations in the nM-range causing complete blockade of platelet proteasome activity do not affect agonist induced platelet aggregation, indicating that the level of platelet proteasome activity is not directly linked with the induction of platelet aggregation. Bortezomib in the µM-range may tamper platelet aggregation, possibly due to unspecific and toxic effects.
authors: Institute of Transfusion Medicine and Haemotherapy, University of Wuerzburg, Oberduerrbacher Straße 6, D-97080 Wuerzburg, Germany. Electronic address: koessler_j@ukw.de.
authors: Juergen
authors: J
authors: Koessler
authors: Institute of Transfusion Medicine and Haemotherapy, University of Wuerzburg, Oberduerrbacher Straße 6, D-97080 Wuerzburg, Germany. Electronic address: juliaetzel@gmx.de.
authors: Julia
authors: J
authors: Etzel
authors: Institute of Transfusion Medicine and Haemotherapy, University of Wuerzburg, Oberduerrbacher Straße 6, D-97080 Wuerzburg, Germany. Electronic address: Weber_K2@ukw.de.
authors: Katja
authors: K
authors: Weber
authors: Institute of Transfusion Medicine and Haemotherapy, University of Wuerzburg, Oberduerrbacher Straße 6, D-97080 Wuerzburg, Germany. Electronic address: Boeck_M@ukw.de.
authors: Markus
authors: M
authors: Boeck
authors: Institute of Transfusion Medicine and Haemotherapy, University of Wuerzburg, Oberduerrbacher Straße 6, D-97080 Wuerzburg, Germany. Electronic address: Kobsar_A@ukw.de.
authors: Anna
authors: A
authors: Kobsar
mesh_terms: D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D001798:Blood Proteins / Q000378:metabolism; D000069286:Bortezomib / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D005260:Female; D006801:Humans; D008297:Male; D010974:Platelet Aggregation / Q000187:drug effects; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology*; D054875:Ubiquitination / Q000187:drug effects; D055815:Young Adult
chemical_list: D001798:Blood Proteins; D061988:Proteasome Inhibitors; D000069286:Bortezomib; D046988:Proteasome Endopeptidase Complex
keywords: Adenosine 5′-diphosphate (PubChem CID: 6022); Aggregation; Bortezomib; Bortezomib (PubChem CID: 387447); Platelet; Proteasome; TRAP-6 (PubChem CID: 9831933); Ubiquitination