Background: To mediate hemostasis, platelets use energy-dependent processes (e.g., activation, aggregation, granule secretion, clot formation and contraction), yet it is unclear what metabolic fuels and energy-producing pathways are required for which for platelet function. Platelets have metabolic flexibility, using several fuels (glucose, glycogen, etc.) and switching between glycolysis and oxidative phosphorylation (OxPhos); however, the relative roles of these ATP-generating processes is unclear.

Aims: To understand the role of platelet bioenergetics and mitochondrial function in hemostasis.

Methods: To study clot contraction, we developed a continuous imaging assay which yields multiple kinetic parameters: lag time, rate, extent, and the area under the curve (AUC). Metabolic inhibitors and a platelet-specific TFAM (Transcription Factor A Mitochondrial) deletion were used to probe the importance of platelet bioenergetics and mitochondrial function.

Results: Platalet-specific TFAM-deficient mice showed defective clot contraction
We demonstrated metabolic flexibility using our clot contraction assay and metabolic inhibitors. Clot contraction was inhibited by using glycolysis inhibitor (2-Deoxyglucose, 2DG), which was rescued by adding the downstream metabolite pyruvate. Clot contraction was also inhibited by OxPhos inhibitor (oligomycin) and glycogen phosphorylase inhibitor (CP 316819) indicating that all three processes fuel clot contraction. To further investigate the role of OxPhos and mitochondrial to platelet function, we used TFAM-/- platelets (TFAMflox/flox::PF4Cre+) mice. Clot contraction with TFAM KO platelets showed defective rate, extent, and AUC at low thrombin concentration (5 mU/mL) when compared to wild type controls, but showed similar contraction at higher (20 mU/mL) (Fig A, B, C). When clot contraction was measured in the presence of a glycolysis 2-DG and CP 316819, platelets from TFAM mice showed decreased rate and extent of clot contraction compared to control (Fig D, E, F).  

Conclusions: Our data show that glycolysis, glycogen breakdown and OxPhos all contribute to the energy pool for clot contraction. The data confirm platelets’ metabolic flexibility and show that mitochondrial bioenergetics is important for function.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/understanding-the-role-of-mitochondria-in-platelet-function/