PB0883 - Defining the Role of Hepcidin and Ferroportin Interactions in Regulating Platelet Function

Background: Systemic iron homeostasis is tightly regulated by the interaction of hepcidin with the iron export protein ferroportin (FPN, SLC40A1). Ferroportin is expressed by hepatocytes, enterocytes, and macrophages; however, the extent to which, and potential role of ferroportin expression by platelets has not yet been reported. While iron status and platelet function are clinically interrelated, the interaction between iron regulatory mechanisms and platelet physiology remain poorly understood.

Aims: Here, we aim to determine: (1) whether platelets express ferroportin and, (2) how hepcidin-ferroportin interactions affect platelet function.

Methods: We evaluated ferroportin protein expression in human platelets with flow cytometry, Western blotting, and fluorescence microscopy methods. Through ex vivo platelet activation experiments, we examined biochemical and physiologic responses of platelets in the presence of the bioactive 25-amino acid peptide hepcidin together with established platelet agonists and inhibitors.

Results: Flow cytometry and Western blot analysis both detected ferroportin expression on human platelets. Ex vivo, hepcidin treatment resulted in decreased detection of ferroportin expression on platelets. Fluorescence microscopy analysis likewise visualized ferroportin and hepcidin on platelets, as well as within platelet granules. Ex vivo, physiologic concentrations of hepcidin reduced glycoprotein IIb/IIIa (GPIIb/IIIa)-mediated platelet spreading on fibrinogen and reduced GPIIb/IIIa expression on the platelet surface in a manner related to intracellular immunoreceptor tyrosine-based activation motif (ITAM) signaling downstream of platelet GPVI.

Conclusion(s): Taken together, our results suggest that ferroportin is expressed on platelets, and that interactions between hepcidin and ferroportin may regulate platelet function in the context of systemic iron sensing and trafficking. Future studies will investigate hypotheses around the hepcidin-ferroportin axis in the pathogenesis of iron-dependent changes in platelet function and hemostasis.