DOI

10.1111/jth.12422

Abstract

Background

Intravascular hemolysis occurs after blood transfusion, in hemolytic anemias, and in other conditions, and is associated with hypercoagulable states. Hemolysis has been shown to potently activate platelets in vitro and in vivo, and several mechanisms have been suggested to account for this, including: (i) direct activation by hemoglobin (Hb); (ii) increase in reactive oxygen species (ROS); (iii) scavenging of nitric oxide (NO) by released Hb; and (iv) release of intraerythrocytic ADP.

Objective

To elucidate the mechanism of hemolysis-mediated platelet activation.

Methods

We used flow cytometry to detect PAC-1 binding to activated platelets for in vitro experiments, and a Siemens' Advia 120 hematology system to assess platelet aggregation by using platelet counts from in vivo experiments in a rodent model.

Results

We found that Hb did not directly activate platelets. However, ADP bound to Hb could cause platelet activation. Furthermore, platelet activation caused by shearing of red blood cells (RBCs) was reduced in the presence of apyrase, which metabolizes ADP to AMP. The use of ROS scavengers did not affect platelet activation. We also found that cell-free Hb enhanced platelet activation by abrogating the inhibitory effect of NO on platelet activation. In vivo infusions of ADP and purified (ADP-free) Hb, as well as hemolysate, resulted in platelet aggregation, as shown by decreased platelet counts.

Conclusion

Two primary mechanisms account for RBC hemolysis-associated platelet activation: ADP release, which activates platelets; and cell-free Hb release, which enhances platelet activation by lowering NO bioavailability.

Document Type

Post-print Article

Publication Date

12-2013

Comments

Alternate Author Names: C.R. Carlisle or Christine R. Carlisle

Publisher Statement

Copyright © 2010 International Society on Thrombosis and Haemostasis. Article first published online: 10 DEC 2013. DOI: 10.1111/jth.12422.

The definitive version is available at: http://onlinelibrary.wiley.com/doi/10.111

Full citation:

Helms, C. C., M. Marvel, W. Zhao, M. Stahle, R. Vest, G. J. Kato, J. S. Lee, G. Christ, M. T. Gladwin, R. R. Hantgan, and D. B. Kim-Shapiro. "Mechanisms of Hemolysis-Associated Platelet Activation." Journal of Thrombosis and Haemostasis 11, no. 12 (December 10, 2013): 2148-154. doi:10.1111/jth.12422.

Download

Share

COinS