The mitochondrial deacetylase SIRT3 is nonessential for cyclophilin D-dependent procoagulant platelet formation in mice

Sirtuin 3 (SIRT3) is a nicotinamide adenine dinucleotide (NAD)-dependent mitochondrial deacetylase that regulates protein acetylation and maintains mitochondrial homeostasis in nucleated cells. By deacetylating cyclophilin D (CypD), SIRT3 limits mitochondrial permeability transition pore (mPTP) opening and protects against mitochondrial dysfunction. Although SIRT3 is present in murine and human platelets, its contribution to platelet mitochondrial regulation and procoagulant platelet formation remains unknown. This study investigated whether platelet SIRT3 modulates CypD-dependent procoagulant platelet formation. Platelets obtained from platelet-specific Sirt3 knockout mice (Sirt3plt−/−) and littermate controls (Sirt3plt+/+) were analyzed under resting conditions and after activation with CRP-XL and thrombin. Flow cytometry was used to analyze platelet (activation) markers and procoagulant platelet formation, and mitochondrial respiration was assessed using a Seahorse extracellular flux analyzer. Platelets lacking SIRT3 showed no alterations in basal or agonist-stimulated mitochondrial respiration. Likewise, platelet Sirt3 deletion did not affect the generation of procoagulant platelets in response to strong dual agonist stimulation. These findings indicate that, despite its role in regulating mPTP opening in nucleated cells, platelet SIRT3 is not required for procoagulant platelet formation, suggesting that platelets rely on distinct mechanisms for mPTP regulation.