270 - IκB kinase 2 (IKK2) is not essential for platelet activation (ID 881)
Abstract
Background and Aims
It has been reported that IκB kinase 2 (IKK2), the central enzyme of the inflammatory NF-κB pathway, is involved in platelet activation as megakaryocyte/platelet-specific deletion of exons 6/7 of IKK2 resulted in platelet degranulation defects and prolonged bleeding. We aimed to investigate the role of IKK2 in platelet physiology in more detail, using a platelet-specific IKK2 knockout via excision of exon 3, which comprises the active site of the enzyme.
Methods
Mice expressing Cre recombinase downstream of the megakaryocyte-specific Pf4-promoter were crossed with mice, where exon-3 of IKK2 was flanked by loxP sites. Excision was verified on the genomic level and deletion on the level of RNA and protein. Platelet function was investigated in vitro by aggregometry, flow cytometry and degranulation assays; as well as in vivo by measuring bleeding times and thrombus formation induced in mesenteric arteries by FeCl3. A potential role of IKK2 in human platelets was studied by applying the specific IKK2 inhibitors TPCA-1 and BMS-345541 followed by flow cytometry.
Results
Platelets with a complete deletion of IKK2 did not show any functional impairment in vivo or in vitro. Bleeding time and thrombus formation were not increased. Moreover, platelet aggregation, GPIIb/IIIa activation and degranulation were unaltered. Pharmacological inhibition of IKK2 with TPCA-1 or BMS-345541 did not affect activation of murine or human platelets over a wide concentration range.
Conclusions
In contrast to previous claims, our results imply that IKK2 is not required for platelet function. However, this does not exclude an effect of inflammation or active IKK2 on platelet reactivity.
