Background: Inflammation plays an important role in the development of thrombosis. Therefore, studying effects of inflammatory cytokines on platelet-bearing von Willebrand factor (VWF) clearance by a disintegrin-like and metalloproteinase with thrombospondin type I repeats 13 (ADAMTS13) as the first step in thrombus formation is pathophysiologically significant.

Aims: This study investigated the mechanism by which interleukin-6 (IL-6)-induced platelet characteristic changes are involved in the regulation of ultra-large VWF (ULVWF)-platelet strings by ADAMTS13.

Methods: For this, we used platelets washed after incubation with IL-6 and compared their capability to form platelet-bearing ULVWF strings with that of mock-treated platelets following perfusion through the microfluidic channel with a basal surface lined with stimulated endothelial cells.

Results: The perfusion of IL-6-treated platelets significantly increased the formation of ULVWF-platelet strings and decreased their cleavage by ADAMTS13 in Figure 1. We found that platelets treated with IL-6 increased the phosphorylation of the serine/threonine kinase Akt and extracellular signal-regulated protein kinases 1/2. To examine whether the activation of the IL-6-induced signaling pathway in platelets regulates the formation and cleavage of ULVWF-platelet strings by ADAMTS13, IL-6-treated and untreated platelets were incubated with inhibitors of the IL-6 signaling pathway before perfusion through the microfluidic channel. Treatment of IL-6-treated platelets with either the phosphoinositol-3 kinase inhibitor LY294002 or the mitogen-activated protein kinase kinase inhibitor U0126 reduced the formation of platelet strings and restored the ability of ADAMTS-13 to cleave IL-6-treated platelet strings compared to the group treated with IL-6 alone. Furthermore, IL-6 increased the phosphorylation of the intracellular adaptor molecule 14-3-3 zeta, which is involved in regulation of VWF binding to the glycoprotein Ib-IX receptor on platelets. The 14-3-3 antagonist R18 significantly enhanced ADAMTS-13 cleavage of IL-6-treated platelet strings in Figure 2.

Conclusions: These results indicate that IL-6 increased the formation of ULVWF-platelet strings and reduced their cleavage by ADAMTS13.

[Formation of IL-6-treated platelet-ULVWF strings and clearance by ADAMTS13]

[Involvement of 14-3-3 in the cleavage of ULVWF-platelet strings by ADAMTS13 under flow conditions]

« Back to ISTH 2020 Congress

ISTH Congress Abstracts - https://abstracts.isth.org/abstract/the-effect-of-il-6-primed-platelets-on-adamts13-mediated-clearance-of-platelet-bearing-ulvwf-and-its-mechanism/