Role of Mitochondrial Impairment in Sepsis-Induced Platelet Activation

Objectives: Sepsis-induced mitochondrial impairment has been described in different organs, in both animal models and humans. Excessive radical oxygen species (ROS) could be involved in this phenomenon. As a result, antioxidants have been proposed as a potential therapeutic strategy, although results remain controversial. Platelet hyperactivation is considered a central pathogenic mechanism in the development of sepsis-induced organ damage. In this study, we aimed to determine whether mitochondrial dysfunction contributes to platelet hyperactivation during sepsis. We also evaluated the effect of ROS scavenging using the mitochondria-targeted antioxidant MitoTEMPO. Design: Laboratory investigation. Setting: University Hospital. Patients and Subjects: Patients with sepsis/septic shock ( n = 3/7), nonseptic burn patients ( n = 10), and healthy control subjects ( n = 10). Interventions: Platelet mitochondria and isolated platelets from healthy donors were treated in vitro with plasma from patients with sepsis/septic shock and healthy subjects, before and after preincubation with MitoTEMPO. Measurements and Main Results: We measured platelet oxygen consumption rates in isolated human platelets using the Seahorse Extracellular Flux Analyzer. Platelet mitochondrial respiratory chain enzyme activity was measured in mitochondria-enriched fractions by spectrophotometry. Platelet aggregation in platelet-rich plasma was analyzed using light-transmission aggregometry, and leukocyte-platelet adhesion in whole blood by flow cytometry. We found that incubating platelets with septic plasma significantly reduced basal, maximal, and adenosine triphosphate-linked oxygen consumption rate. Incubation of platelet mitochondria with septic plasma also reduced platelet Complex I activity, compared with healthy plasma or plasma from nonseptic burn patients. This decrease was associated with an increase in Epinephrine-induced platelet activation. Preincubating platelets with the mitochondria-selective ROS scavenger MitoTEMPO significantly reversed these effects. Conclusions: Our results show that the mitochondria-selective ROS scavenger MitoTEMPO prevents mitochondrial dysfunction and enhances platelet activation induced by septic plasma in human platelets in vitro. This may help in designing new therapeutic approaches to prevent sepsis-induced organ damage mediated by mitochondrial dysfunction and platelet hyperactivation.