Abstract 15748: Platelet Specific Knockout of Mitochondrial Superoxide Dismutase (Sod2) Impairs Mitochondrial Function and Increases Convulxin-Stimulated Platelet Activation
Humans or rodents with type 2 Diabetes mellitus or obesity develop increased thrombosis that is associated with markers of increased oxidative stress in platelets. Additionally, incubation of platelets in high glucose increases mitochondrial reactive oxygen species (ROS) production. The relationship between mitochondrial ROS and platelet activation is unknown. To test the hypothesis that increased mitochondrial ROS in platelets will impair mitochondrial function and increase platelet activation, we generated mice with platelet specific knockout of mitochondrial superoxide dismutase (Sod2) by crossing platelet factor/chemokine receptor 4 Cre (Pf4Cre) mice with Sod2 floxed mice. Sod2 levels were decreased in platelets of KO mice (Sod2/GAPDH: KO 0.7±0.1 AU; Control 4.5±1.2 AU, p=0.006). Mitochondrial oxygen consumption rates (OCR) measured using the Seahorse Flux Analyzer were unchanged in non-stimulated KO platelets relative to control platelets (OCR: Baseline KO 152±55, Control 146±49; Oligomycin KO 56±32, Control 62±30; FCCP KO 202±59, Control 172±42; Rotenone/Antimycin A KO 82±38, Control 78±34; p>0.05). In contrast, when platelets were stimulated with thrombin, OCR increased in controls, but not in knockouts (OCR: Baseline KO 103±37, Control 256±93; Oligomycin KO 31±18, Control 83±30; FCCP KO 94±33, Control 249±41; Rotenone/Antimycin A KO 23±16, Control 88±28; p<0.05). Thus Sod2 deficient platelets exhibit impaired respiratory activity upon stimulation. To determine if these bioenergetics changes altered platelet activation, platelets were incubated in vitro with the glycoprotein VI receptor agonist convulxin and JonA binding was monitored using flow Cytometry. Sod2 deficient platelets displayed increased sensitivity towards convulxin, vs. controls (Convulxin 80ng/mL-KO 57±24, Control 39±23, p<0.05; Convulxin160ng/mL - KO 99±14, Control 81±19, p<0.05). However, in vivo analysis of tail bleed times (KO 71+11 seconds, Control 60+ 21 seconds, p=0.40) were not significantly different between groups. Thus Sod2 deficiency impairs platelet mitochondrial function and increases activation of platelets in the presence of convulxin indicating a link between mitochondrial function and platelet activation.
- © 2013 by American Heart Association, Inc.